URBANEARS Plattan Over-Ear Headphones - Clover 40mm Handmade Drivers - Allow for rich, secluded sound The ZoundPlug - It's actually not a plug, but rather a socket that allows your friend to plug into your earcap and listen to the same thing as you are listening toSpecifications Drivers - 40 mm handmade drivers Frequency Response - 20Hz-20kHz Impedance - 60 ohms