Hamilton Electronics HA2V - Super affordable personal educational headphone featuring in-line volume control and Hamlton's exclusive patented ASM automatic stereo/mono technology. ASM allows these headphones can be safely used with virtually all school audio equipment. Never longer worry about mismatching headphones between different sources and damaging ears or equipment. No switches to set or special plug adapters to change - the headphone knows if it is plugged into a stereo or mono system and automatically adjusts! Operates in 1/8 inch stereo, 1/8 inch mono, 1/4 inch stereo or 1/4 inch mono modes. Built with kid's health and safety in mind, these are the first headphones designed to combat the spread of head lice in schools. Each headphone comes in its own heavy-duty, write-on, reclosable bag. When sealed in the bag, lice is killed in 24-48 hours without the use of chemicals.