Califone 8200HP-20L Classroom 20-Pack Digital Stereo Headphones This twenty-pack of lightweight stereo headphones is ideal for casual listening. Its adjustable headband, on-ear earcups and recessed wiring make it a convenient and comfortable headphone for multipurpose classroom applications, computer labs, libraries and listening centers. Their 3.5mm plugs fit all computers, tablets (such as iPads and Chromebooks) and smartphones, making it an economical alternative for online assessments. Key Features Fully adjustable, lightweight headband fits all students Recessed wiring resists prying fingers for classroom safety Soft and comfortable ear cushions On-ear ambient noise-reducing earcups Windows and Mac compatibility Permanently attached cord Connects with MP3 players, tablets, media players and computers Specifications Diaphragm: 30mm Mylar Driver: Ferrite magnet Impedance: 32 Ohms ± 10% Frequency Response: 20-20,000 Hz Sensitivity: 102dB SPL ± 3dB at 1kHz Normal Input: 40 milliwatts Channel Balance: 3 dB at 1 kHz S.P.L Input Connection: 3.5mm, black jacketed, nickel plated stereo Cord: 3 feet, 3.5mm plug Weight: 3 oz.