Convert standard 2.1 to 3.5 (for some DOD, RAT, Electro-Harmonix, etc) 1 2.1 female socket, 1 male r/a 3.5 plug; about 3" long. Used to power 3.5 pedals thru PedalSnake PLines. If these pedals are used with their own 3.5 power supply--so also see Power Plug Adapters for Supplies.