C12B, Switchcraft 1/4" Open Frame Jack, 3-Conductor, MIL number M641/5-1, .210 inch inside dia. Mates with 480 plug. Non-turn locating pin keys the jack to the mounting surface. M641/5-1- note as of Jan 2014 C12B is no longer available.
Please order new part number Switchcraft C12BZ. Switchcraft C12BZ is similar to the C12B but not mil spec or mil marked.