All male connectors (plugs) of this family feature a 13.2 mm diameter metal shield with a notch that restricts the orientation in which plug and socket can mate.

A range of connectors of the same form that differ only in their pin configuration exist and have been standardized.  There are seven common patterns, with pins numbering from three to eight.  Some pin configurations are shown below.

These plugs consist of a circular shielding metal skirt protecting a number of straight round pins.  The skirt is keyed to ensure that the plug is inserted with the correct orientation and to prevent damage to the pins. The basic design also ensures that the shielding is connected between socket and plug prior to any signal path connection being made.  

Warner inline solution heaters and CC-28 cable, for instance, use DIN connectors.