Affordable School Headphones at Learning Headphones

2021AV is a lightweight headphone that is comfortable for students of all ages. Designed with cobalt transducers to perform with surround sound quality. Works with a variety of devices. Includes 6 foot CaliTuff Cord that is braided and PVC covered to resist chewing, cutting or separation. Cord is reinforced where it attaches to the ear cup, has convenient inline volume control and ends with a 3.5mm, stereo plug. Features: Lightweight for added comfort for all ages Cobalt transducers provide superior sound quality 3 year warranty 3.5mm plug Specifications: Plug Type: 3.5mm Allergens: Contains PVC Brand Name: Califone Cord Length: 6 ft Material: ABS Plastic / PVC

Available colors (200-pack): Blue Green Orange Purple HamiltonBuhl® Personal On-Ear Stereo Headphone, BLUE — 200 Pack Equip labs and testing rooms with a budget-smart 200-pack of HamiltonBuhl personal on-ear headphones. The color-coded Blue shells simplify set management by room or grade, while replaceable foam earpads and the 5' Dura-Cord™ chew/kink/knot-resistant cable hold up to daily school use. Key Features Bulk 200-pack: Ideal for district rollouts and exam rooms. On-ear comfort: Lightweight fit with replaceable foam pads. 5' Dura-Cord™: PVC-jacketed, braided nylon—resists chewing, kinks, and knots. Anti-lice storage bag: Heavy-duty, moisture-resistant bag for each unit; kills lice in 24–48 hours when sealed—no chemicals. 3.5 mm stereo plug: Thin 120° barrel fits most cases; ready for computers, carts, and players. Listening-only: Headphones (no microphone)—perfect for assessments and read-alongs. Specifications Form factor: Personal on-ear, stereo Drivers: 30 mm Connection: 3.5 mm TRS (120° thin barrel) Cable: 5' Dura-Cord™ (PVC-jacketed, braided nylon) Earpads: Replaceable foam Color / Qty: Blue / 200 headphones Extended specs (tap to view) Frequency response: 50 Hz – 16,000 Hz Impedance: 32 Ω Sensitivity: 90 dB ±4 dB Compliance: Prop 65 Hygiene: Anti-lice, moisture-resistant, reclosable bag (1 per unit) Classroom Tips Number units 1–30 per cart/shelf for quick distribution and returns. Keep replacement earpads on hand to extend fleet life. Store with racks or bins and use device-safe wipes for fast end-of-day cleanup. Compare Your Options Model Connection Mic Best For Personal On-Ear (this page) 3.5 mm No Listening-only testing & labs AE-35 USB-C Headphone USB-C No USB-C fleets, assessments AC-155 Mobile Headset 3.5 mm TRRS Yes (boom) Chromebook carts with combo jacks AC-155 USB Headset USB-A Yes (boom) USB-A desktops/labs Buying for a district? We accept POs and offer volume pricing. Request a quote.

Choose your connection: 3.5 mm TRRS (analog) or USB-C (digital). USB-C includes onboard digital audio and is priced higher. For the: AVID WonderEars AP-400 Ages: 4–9 (child-sized on-ear fit) Mic: KidCom™ built-in microphone for clear speech Safety: 85 dB volume limiter Colors: White/Green, White/Orange Warranty: 2 years AVID WonderEars™ AP-400 is a kid-friendly classroom headset designed for ages 4–9. Soft on-ear cushions and an easy-adjust headband keep students comfortable, while the break-resistant KidCom™ microphone captures clear voices in lessons and assessments.Pick the right connector 3.5 mm TRRS — best for devices with a combined headset jack (many Chromebooks, laptops, desktops). USB-C — best for devices without an audio jack or when you want a digital audio connection. USB-C is priced higher due to the integrated audio interface. Why classrooms like AVID WonderEars AP-400 Safer listening with an 85 dB limiter KidCom™ mic supports clear speech during reading apps, language practice, and testing Comfort fit for child head sizes; soft on-ear pads Durable design for school environments 2-year warranty CompatibilityWorks with Chromebooks, laptops, and tablets. Choose 3.5 mm TRRS for a headset jack or USB-C for devices that support USB-C audio. Always check your device ports.Care & HygieneWipe ear cushions and headband with non-abrasive, alcohol-free wipes after use; allow to fully dry before storage. Assigning headsets helps reduce sharing.Tech specs Age range 4–9 Connection 3.5 mm TRRS (analog) or USB-C (digital) Microphone KidCom™ built-in mic Listening safety 85 dB limiter Ear style On-ear, soft cushions Colors White/Green, White/Orange Warranty 2 years FAQIs this headset safe for kids?Yes. WonderEars AP-400 includes an 85 dB limiter and a child-sized on-ear fit for ages 4–9.Does it work with Chromebooks?Yes. Pick 3.5 mm TRRS for models with a headset jack, or USB-C for devices that support USB-C audio. Check your device ports to confirm.

The LH-06PS is one of our best‑selling testing headphones for schools and offices, featuring 360°–swivel earpieces for a fully customizable fit. Built to last, it’s perfect for classrooms, call centers, training labs, and any environment where comfort and reliability matter. Bulk School On-Ear Headphones LH-06PS - 1000 PackKey Features Swivel Earpieces: Adjustable 360° for personalized comfort and single‑ear monitoring Affordable design for testing and audio apps. Not intended for extended daily use Lightweight Design: Under 2 oz for fatigue‑free wear Universal Compatibility: Standard 3.5 mm jack works with PCs, tablets, and mobile devices Specifications: Driver: 30 mm dynamic Frequency Response: 20 Hz – 20 kHz Impedance: 32 Ω ± 15% Cable Length: 4 ft (1.2 m) Connector: 3.5 mm 

The Bulk School On-Ear Headphones LH-06PS 100 Pack is one of our best‑selling packs for testing headphones for schools and offices, featuring 360°–swivel earpieces for a fully customizable fit. Built to last, it’s perfect for classrooms, call centers, training labs, and any environment where comfort and reliability matter.Key Features Swivel Earpieces: Adjustable 360° for personalized comfort and single‑ear monitoring Affordable design for testing and audio apps. Not intended for extended daily use Lightweight Design: Under 2 oz for fatigue‑free wear Universal Compatibility: Standard 3.5 mm jack works with PCs, tablets, and mobile devices Specifications: Driver: 30 mm dynamic Frequency Response: 20 Hz – 20 kHz Impedance: 32 Ω ± 15% Cable Length: 4 ft (1.2 m) Connector: 3.5 mm 

Boost classroom engagement with durable, affordable audio solutions. The Califone CA-2 On-Ear Headphones Lightweight On-Ear Headphones (1000-Pack) are designed specifically for schools and educational programs, offering a reliable listening experience for students across all grade levels. With a universal 3.5mm plug, these headphones are compatible with desktops, laptops, tablets, and Chromebooks—perfect for testing, multimedia lessons, language labs, and remote learning. Crafted for comfort and functionality, each headphone features a lightweight, on-ear design, adjustable headband, and noise-reducing earcups to help students stay focused. The rugged ABS plastic construction ensures they hold up to daily classroom use, while the affordable bulk pricing makes it easy for schools and districts to equip entire classrooms or testing centers efficiently.Key Features: Noise-Reducing Ear Cups: The on-ear foam cushions help reduce exterior sounds, allowing students to focus on their lessons without distractions. Ideal for both in-classroom use and online learning. Comfort for Long Wear: Designed for extended listening, these headphones are lightweight and comfortable, ensuring students can wear them for hours without discomfort. Adjustable Fit: The flexible headband adjusts to fit most students, providing a secure and personalized fit for all head sizes. The recessed wiring keeps cords neatly out of the way for a tidy and hassle-free experience. Durable & Safe Design: Made from durable ABS plastic, these headphones are built to withstand daily classroom use while offering reliable performance. Convenient Storage: The headphones come with a resealable storage bag to keep them protected and organized when not in use, making them perfect for shared environments. Specifications: Plug Type: 3.5mm stereo plug for wide device compatibility Cord Length: 5-1/2 feet for flexible movement Material: ABS Plastic for durability Size: Adjustable headband for a comfortable fit Allergens: Contains PVC Warranty: 90 day warranty for school use - unlike headphones purchased at consumer electronics stores whose warranties would be voided if used in schools. Order your Califone Lightweight Headphones today and enhance your students' learning environment with comfort and clarity!

Boost classroom engagement with durable, affordable audio solutions. Califone CA-2 Lightweight On-Ear Headphones 3.5mm 500-Pack are designed specifically for schools and educational programs, offering a reliable listening experience for students across all grade levels. With a universal 3.5mm plug, these headphones are compatible with desktops, laptops, tablets, and Chromebooks—perfect for testing, multimedia lessons, language labs, and remote learning.Crafted for comfort and functionality, each headphone features a lightweight, on-ear design, adjustable headband, and noise-reducing earcups to help students stay focused. The rugged ABS plastic construction ensures they hold up to daily classroom use, while the affordable bulk pricing makes it easy for schools and districts to equip entire classrooms or testing centers efficiently.Key Features: Noise-Reducing Ear Cups: The on-ear foam cushions help reduce exterior sounds, allowing students to focus on their lessons without distractions. Ideal for both in-classroom use and online learning. Comfort for Long Wear: Designed for extended listening, these headphones are lightweight and comfortable, ensuring students can wear them for hours without discomfort. Adjustable Fit: The flexible headband adjusts to fit most students, providing a secure and personalized fit for all head sizes. The recessed wiring keeps cords neatly out of the way for a tidy and hassle-free experience. Durable & Safe Design: Made from durable ABS plastic, these headphones are built to withstand daily classroom use while offering reliable performance. Convenient Storage: The headphones come with a resealable storage bag to keep them protected and organized when not in use, making them perfect for shared environments. Specifications: Plug Type: 3.5mm stereo plug for wide device compatibility Cord Length: 5-1/2 feet for flexible movement Material: ABS Plastic for durability Size: Adjustable headband for a comfortable fit Allergens: Contains PVC Warranty: 90 day warranty for school use - unlike headphones purchased at consumer electronics stores whose warranties would be voided if used in schools. Order your Califone Lightweight Headphones today and enhance your students' learning environment with comfort and clarity!

The TW300 REVO 100 percent over-ear headphone featuring superior sonics and unique ear cup swivel technology to perfectly fit each individual listener combines state of the art technology with audio excellence to create an affordable, adaptable, and satisfying listening experience. The thick and luxurious ear cushions gently surround and insulate the ear in 360 to provide unbeatable sound quality and minimize background noise. A sleek design couples with custom-tuned 40mm drivers and easy-to-remove and -replace modular ear cushions and cables to make the TW300 REVO an innovative headphone that will last the test of time.  Get a quote today for the TWT Audio TW300 REVO Headphones. Features: Ergonomically sleek structure Luxurious 24mm thick seamless ear cushion Acoustically tuned and ported ear cups Superior sound quality from custom 40mm driver Innovative and durable structuring 3.5mm TRS jack Two Year Warranty Technical Description: Color Black Specifications 3.5 mm Pack Box Size 8x3.25x8in

The TWT Audio ERGO TW102 Headphone at Learning Headphones exclusively by TWT Audio from the ground up with the singular goal of creating a better sounding, more comfortable on-ear headphone. Informed by our professional classroom experience, the ERGO provides sustained comfort, superior sound, and TWT Audio's signature durability. Featuring ergonomically angled earcups and an optimized audio curve, ears remain protected from the stress of compression and strain of damaging frequencies over longer listening periods. With 30mm drivers delivering exceptional sound quality, the TW100 is the ideal on-ear headphone for school testing and everyday usage.Technical Description: Color Black Specifications USB-A Pack Box Size 6.875x2.375x7in

Califone 3068AV-CT Stereo/Mono Headphones – Versatile, Durable, and Ideal for Classroom Learning The Califone 3068AV-CT Stereo/Mono Headphones are the perfect solution for educators looking for flexibility, durability, and quality sound. Designed to support blended learning, these headphones allow students to easily switch between stereo and mono audio, making them ideal for a variety of learning activities—whether it's language learning, speech pathology, or digital learning. Key Features: Switchable Stereo/Mono Functionality: The Califone 3068AV-CT headphones feature an easy-to-use stereo/mono switch, giving teachers and students the flexibility to switch between monaural content for activities like ELL/ELD and speech therapy to stereo sound for computer-based tasks, online learning, or music appreciation classes. This versatility makes the headphones perfect for a wide range of classroom applications. Dual Volume Controls: Equipped with dual volume controls on each earcup, these headphones allow students to adjust the sound to their preference, ensuring a comfortable listening experience. Durable & Break-Resistant Design: Made from rugged ABS plastic, the headband and earcups are built to withstand heavy use in busy school environments, ensuring these headphones stand up to the demands of daily classroom activities. Comfortable & Hygienic: The hypoallergenic earpad covers and replaceable padded leatherette cushions provide comfort and are easy to clean, making these headphones safe and hygienic for all students. Noise-Reducing Earcups: The noise-reducing earcups minimize ambient noise, allowing students to enjoy audio at a lower volume. This not only improves listening quality but also helps protect students’ hearing, as recommended by audiologists. Versatile Plug Options: The snap-on adapter with dual plug sizes ensures that these headphones are compatible with any media player, including smartphones, tablets, and computers, making them a great fit for a range of devices in both traditional and digital learning settings. Specifications: Cord Length: 10 feet of 2-layer straight cord for flexibility and mobility Plug Type: 3.5mm plug for universal compatibility Warranty: 3-year warranty specifically for school use, unlike consumer electronics headphones whose warranties may be voided in educational settings Weight: Lightweight for comfort during extended use Why Choose Calilfone 3068AV-CT Headphones? The Califone 3068AV-CT Stereo/Mono Headphones offer exceptional value and versatility for classrooms, libraries, and listening centers. With a stereo/mono switch, dual volume controls, and noise-reducing earcups, these headphones meet the diverse needs of modern education, from Common Core curriculum to 21st-century learning. Built for durability and comfort, the 3068AV-CT is designed to withstand daily school use while providing high-quality sound and protection for students’ hearing. Order your Calilfone 3068AV-CT Headphones today and provide your students with the flexibility, comfort, and performance they need to succeed in the classroom!

2021AVB-USB is a lightweight headphone that is comfortable for students of all ages. Designed with cobalt transducers to perform with surround sound quality. Convenient USB plug works with a variety of devices. Includes 6 foot CaliTuff Cord that is braided and PVC covered to resist chewing, cutting or separation. Cord is reinforced where it attaches to the ear cup, has convenient inline volume control and ends with a 3.5mm, stereo plug. Features: Lightweight for added comfort for all ages Cobalt transducers provide superior sound quality 3 year warranty USB plug Inline volume control Foam-filled, leatherette ear cushions Over-ear, polypropylene plastic ear cups resistbreakage in high-use environments Specifications: Plug Type: USB Allergens: Contains PVC Brand Name: Califone Cord Length: 6 ft Description: Stereo Headphone with USB Plug Material: ABS Plastic / PVC

Available colors (200-pack): Blue Green Orange Purple HamiltonBuhl® SchoolMate™ HA2 Headphones — GREEN, 200 Pack Outfit testing rooms and labs with a budget-smart 200-pack of SchoolMate™ HA2 on-ear headphones. Color-coded Green shells make class set management easy, while replaceable foam earpads and the 5' Dura-Cord™ chew/kink/knot-resistant cable stand up to daily school use. Key Features Bulk 200-pack: Ideal for district rollouts and exam rooms. On-ear comfort: Lightweight fit with replaceable foam pads. 5' Dura-Cord™: PVC-jacketed, braided nylon—resists chewing, kinks, and knots. Anti-lice storage bag: Heavy-duty, moisture-resistant bag included for each unit; kills lice in 24–48 hours when sealed—no chemicals. 3.5 mm stereo plug: Thin 120° barrel fits most cases; ready for computers, carts, and players. Listening-only: Headphones (no microphone)—perfect for assessments and read-alongs. Specifications Form factor: Personal on-ear, stereo Drivers: 30 mm Connection: 3.5 mm TRS (120° thin barrel) Cable: 5' Dura-Cord™ (PVC-jacketed, braided nylon) Earpads: Replaceable foam Color / Qty: Green / 200 headphones Extended specs (tap to view) Frequency response: 50 Hz – 16,000 Hz Impedance: 32 Ω Sensitivity: 90 dB ±4 dB Compliance: Prop 65 Hygiene: Anti-lice, moisture-resistant, reclosable bag (1 per unit) Classroom Tips Number units 1–30 per cart/shelf for quick distribution and returns. Keep replacement earpads on hand to extend fleet life. Add storage racks/bins and device-safe wipes for fast end-of-day cleanup. Compare Your Options Model Connection Mic Best For HA2 (this page) 3.5 mm No Listening-only testing & labs AE-35 USB-C Headphone USB-C No USB-C fleets, assessments AC-155 Mobile Headset 3.5 mm TRRS Yes (boom) Chromebook carts with combo jacks AC-155 USB Headset USB-A Yes (boom) USB-A desktops/labs Buying for a district? We accept POs and offer volume pricing. Request a quote.

Available colors (200-pack): Blue Green Orange Purple HamiltonBuhl® Personal On-Ear Stereo Headphone, ORANGE — 200 Pack Equip labs and testing rooms with a budget-smart 200-pack of HamiltonBuhl personal on-ear headphones. The color-coded Orange shells simplify set management by room or grade, while replaceable foam earpads and the 5' Dura-Cord™ chew/kink/knot-resistant cable hold up to daily school use. Key Features Bulk 200-pack: Ideal for district rollouts and exam rooms. On-ear comfort: Lightweight fit with replaceable foam pads. 5' Dura-Cord™: PVC-jacketed, braided nylon—resists chewing, kinks, and knots. Anti-lice storage bag: Heavy-duty, moisture-resistant bag for each unit; kills lice in 24–48 hours when sealed—no chemicals. 3.5 mm stereo plug: Thin 120° barrel fits most cases; ready for computers, carts, and players. Listening-only: Headphones (no microphone)—perfect for assessments and read-alongs. Specifications Form factor: Personal on-ear, stereo Drivers: 30 mm Connection: 3.5 mm TRS (120° thin barrel) Cable: 5' Dura-Cord™ (PVC-jacketed, braided nylon) Earpads: Replaceable foam Color / Qty: Orange / 200 headphones Extended specs (tap to view) Frequency response: 50 Hz – 16,000 Hz Impedance: 32 Ω Sensitivity: 90 dB ±4 dB Compliance: Prop 65 Hygiene: Anti-lice, moisture-resistant, reclosable bag (1 per unit) Classroom Tips Number units 1–30 per cart/shelf for quick distribution and returns. Keep replacement earpads on hand to extend fleet life. Store with racks or bins and use device-safe wipes for fast end-of-day cleanup. Compare Your Options Model Connection Mic Best For Personal On-Ear (this page) 3.5 mm No Listening-only testing & labs AE-35 USB-C Headphone USB-C No USB-C fleets, assessments AC-155 Mobile Headset 3.5 mm TRRS Yes (boom) Chromebook carts with combo jacks AC-155 USB Headset USB-A Yes (boom) USB-A desktops/labs Buying for a district? We accept POs and offer volume pricing. Request a quote.

Available colors (200-pack): Blue Green Orange Purple HamiltonBuhl® Personal On-Ear Stereo Headphone, PURPLE — 200 Pack Outfit testing rooms and media labs with a budget-smart 200-pack of HamiltonBuhl personal on-ear headphones. The color-coded Purple shells make it easy to manage sets by room or grade, while replaceable foam earpads and a 5' Dura-Cord™ chew/kink/knot-resistant cable stand up to daily school use. Key Features Bulk 200-pack: Ideal for district rollouts and exam rooms. On-ear comfort: Lightweight fit with replaceable foam pads. 5' Dura-Cord™: PVC-jacketed, braided nylon—resists chewing, kinks, and knots. Anti-lice storage bag: Heavy-duty, moisture-resistant bag for each unit; kills lice in 24–48 hours when sealed—no chemicals. 3.5 mm stereo plug: Thin 120° barrel fits most cases; ready for computers, carts, and players. Listening-only: Headphones (no microphone)—perfect for assessments and read-alongs. Specifications Form factor: Personal on-ear, stereo Drivers: 30 mm Connection: 3.5 mm TRS (120° thin barrel) Cable: 5' Dura-Cord™ (PVC-jacketed, braided nylon) Earpads: Replaceable foam Color / Qty: Purple / 200 headphones Extended specs (tap to view) Frequency response: 50 Hz – 16,000 Hz Impedance: 32 Ω Sensitivity: 90 dB ±4 dB Compliance: Prop 65 Hygiene: Anti-lice, moisture-resistant, reclosable bag (1 per unit) Classroom Tips Number units 1–30 per cart/shelf for quick distribution and returns. Keep replacement earpads on hand to extend fleet life. Store with racks or bins and use device-safe wipes for fast end-of-day cleanup. Compare Your Options Model Connection Mic Best For Personal On-Ear (this page) 3.5 mm No Listening-only testing & labs AE-35 USB-C Headphone USB-C No USB-C fleets, assessments AC-155 Mobile Headset 3.5 mm TRRS Yes (boom) Chromebook carts with combo jacks AC-155 USB Headset USB-A Yes (boom) USB-A desktops/labs Buying for a district? We accept POs and offer volume pricing. Request a quote.

Prefer a different accent color? Pick below. Blue Green HamiltonBuhl® Smart-Trek™ Headphone — Green Accents The Smart-Trek deluxe over-ear headphone is built for daily K–12 use with replaceable leatherette cushions, an adjustable, twistable padded headband, and a tough 5' Dura-Cord™ (chew/kink/knot-resistant, PVC-jacketed braided nylon). A thin-barrel, 120° 3.5 mm stereo plug fits most cases, and the in-line volume control makes level tweaks easy for students. :contentReference[oaicite:1]{index=1} Key Features Over-ear comfort: Deluxe, full-cup fit helps reduce classroom noise; replaceable leatherette pads. :contentReference[oaicite:2]{index=2} 3.5 mm stereo plug: Thin-barrel, 120° angle for case-friendly use on carts and laptops. :contentReference[oaicite:3]{index=3} 5' Dura-Cord™: Chew/kink/knot-resistant braided cable for longevity. :contentReference[oaicite:4]{index=4} In-line volume control: Quick level adjustment for students. :contentReference[oaicite:5]{index=5} Classroom-tuned audio: 40 mm drivers deliver clear stereo sound for lessons, testing, and media. :contentReference[oaicite:6]{index=6} Specifications Form factor: Over-ear (stereo), Green accents Drivers: 40 mm Connection: 3.5 mm TRS, 120° thin-barrel plug Cable: 5' Dura-Cord™ (PVC-jacketed braided nylon) Earpads: Leatherette, replaceable Headband: Adjustable, twistable, padded Frequency response: 50 Hz – 20 kHz Impedance: 32 Ω Sensitivity: 100 dB ±4 dB Classroom Tips Number headsets 1–30 per cart/shelf for faster hand-out and return. Keep replacement earpads and device-safe wipes on hand to extend fleet life. Store on racks or bins to prevent cable damage. Compare by Port / Mic Model Port Mic Best For Smart-Trek Headphone (this page) 3.5 mm TRS No Listening-only testing & media AE-35 USB-C Headphone USB-C No USB-C fleets, assessments AC-155 Mobile Headset 3.5 mm TRRS Yes (boom) Chromebook combo-jack carts AC-155 USB Headset USB-A Yes (boom) USB-A desktops/labs Buying for a district? We accept POs and offer volume pricing. Request a quote.

HamiltonBuhl Sack‑O‑Phones with 6 Blue Primo™ Headphones & 3.5 mm Jackbox Set up a robust listening center with this all-in-one kit that includes the Sack‑O‑Phones carry case, 6 blue Primo™ headphones, and a 3.5 mm Galaxy jackbox. Durable and student-friendly, it’s built for classroom audio use. Kit Includes (6) Primo™ headphones — blue color (1) 3.5 mm Galaxy jackbox (5‑way) (1) Sack‑O‑Phones carry bag Why Choose This Bundle? Noise‑reducing ear cups help block ambient distractions Rugged, bite‑resistant Dura‑Cord™ with chew and knot resistance 3.5 mm stereo plug offers universal compatibility (tablets, computers, phones) Sack‑O‑Phones bag keeps devices organized and protected Primo™ Headphone Specs Driver: 30 mm Impedance: 32 Ω Sensitivity: ~100–105 dB ±4 dB Frequency Response: 50 Hz – 20,000 Hz Cushions: Washable leatherette for hygiene Plug: 3.5 mm stereo, 120° angled Cord: 5′ Dura‑Cord™ (chew-resistant, braided, PVC-sleeved) Warranty: 1 year Galaxy™ Jackbox Specs Input: 3.5 mm (1/8″) Outputs: 5 × 3.5 mm (1/8″) Output Power: 100 mW per channel We accept POs and offer volume pricing. Free shipping on orders to the 48 contiguous U.S. All products undergo quality assurance checks.