15 foot (450cm) extension cable terminated with a 1/4 inch (6.3mm) plug and a 1/4 inch (6.3mm) jack. This cable is constructed from the same high quality wire as their headphone cable. For longer lengths the cable may be piggybacked up to 3 cables. Grado guarantees no degradation of sonic quality with Grado headphones while using their extension cable. Prestige 12-conductor version is 12 foot (360cm).