Hamilton Electronics HA2 - Personal educational headphone featuring Hamlton's exclusive patented ASM™ automatic stereo/mono technology. ASM™ allows these headphones to be used with virtually all school audio equipment. Never 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 headphones are 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. Also available with built-in volume control (HA2V); uplgraded leatherette earcushions (MS2L) and leatherette earcushions with volume control (MS2LV).