TE Connectivity AMPMODU Mod IV Center Polarized Receptacle Style Socket Housings. AMPMODU Mod IV center polarized receptacle style socket housings with a 2.54mm centerline. These non-polarized receptacle style socket housings are made from black, flame retardant thermoplastic and have stamped cavity identification part number and date code where size permits. There are two types of keying plugs that can be used with these receptacle style socket housings: stock number ; 681-2644 681-2644 which plugs into the the standard or intermediate pressure receptacle contact and stock number ; 509-2076 509-2076 which plugs directly into the housing.