The MIL-C-38999 Series III connector features the triple start threaded coupling mechanism that offers greater vibration protection. In addition, the series III has metric accessory threads for greater strength and support of backshells. These environmental resistant connectors are 100% "scoop proof". The connectors are available in nine shell sizes, with a choice of two receptacle configurations and a standard plug. There are 55 insert arrangements available, utilising 3 to 128 contacts. Contacts are 22D, 20, 16 and 12 gauge terminated wire sizes 28 through 12 gauge. The hard plastic socket interface features the chamfered conical entry that aids in the proper mating of contacts. The fluorosilicone interfacial seal has conical risers around each pin contact that compress into the socket interface, assuring the seal of the mating surfaces. Three finishes are available for the aluminium shells. Polarisation is machined into the shell (Locksmith Keying).