Introducing the most technically sophisticated and durable headphone ever manufactured by Califone. This set of Mac & PC compatible Titanium™ series stereo headphones will help optimize differentiated learning experiences with breakthroughs in safety, performance, comfort and durability. Built to help students not only learn content material, the HPK-1020 is also designed to teach them about appropriate volume listening levels when using the headphones. By integrating Sentinel Technology™ into the earcups, the volume playback level is restricted to the ASHA-recommended maximum of 85 decibels for safe listening practices (this feature can be disarmed for students with special needs). In addition to filtering the audio volume, each HPK-1020 helps students focus more effectively on the task at hand by blocking the highest amount of ambient (external) noise of any passive headphone which Califone has ever offered. School budgets can't afford equipment that won't last the entire year or cause lost learning time, and that's why the HPK-1020 is built using more rugged ABS plastic (even its cord is thicker than previous models). But longer lasting doesn't automatically mean student comfort, which is why the ear cushions have also been upgraded to be just as long lasting, but feel softer without the accumulated clammy feeling which can come after prolonged use. Includes one WS-CH power charger to charge all four headphones at one time.