Hamilton Electronics HA2V – Super affordable personal educational headphone with in-line volume control. These headphones feature Hamilton’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.