jack 3.5mm to 2.5mm 

Length:1.2m/4 ft

it is compatible with JBL Synchros S700 / S400BT / J56BT / S300 /S300I /S300a / S500 / S700 / E40BT / E30 / E40 / E50BT / S400BT headphones and other 2.5mm port headphones.

jack : 3.5mm Male to 2.5mm Male