The explosive growth of airborne electronic systems in the 1950s demanded high-density connectors with smaller contacts than the size 16 specified in MIL-C-5015. Specification MIL-C-26482 came into being with insert arrangements originally available with sizes 20 and 16 contacts. Size 12 contacts also are a part of the specification now. An improved five-keyway polarizing system and a quick connect/disconnect coupling based on the bayonet coupling design of the Bendix “PT” series was adopted. Series 1 connectors incorporate either solder or crimp front release contacts and Series 2 connectors utilize crimp rear release contacts.