Military (MIL-SPEC) connectors are shell-type connectors are built in accordance with military specifications. Their design takes into account the need to protect the connection from environmental factors, allowing them to be used in military and aerospace applications. Parameters to consider when specifying military (MIL-SPEC) connectors include the number of contacts, contact type, shell size, shell style or gender, coupling type, contact size (AWG), and contact termination options. Compliance with specific MIL-SPEC standards, the inclusion of backshell accessories and a lanyard, and applicability to audio or visual applications are other important considerations. 

Selecting military (MIL-SPEC) connectors requires an understanding of product parameters. The number of contacts are the number of conductive elements in a military connector which mate with a corresponding element to provide an electrical path. Contact types can be either pins or sockets. The main connector housing is called the shell. For circular military (MIL-SPEC) connectors, the shell is cylindrical and available in incremental sizes starting around .375" in diameter. The most common shell sizes are available in .0625 increments starting at shell size 8 (.50) to shell size 36 (2.25). Both the connector and accessory manufacturers use the term "shell size" to designate the size of their respective products. Military (MIL-SPEC) connectors, which use threads to attach backshells, are usually equal to or within .062 of the connector shell size.

Specific military specifications that can be met by military (MIL-SPEC) connectors include, MIL-C-5015, MIL-C-26482, MIL-C-81703, MIL-C-22992, MIL-C-27599, MIL-C-26500, MIL-C-38999, MIL-C-28840, MIL-C-81511, MIL-C-81582, MIL-C-83723, 40M39569, AND 40M38277.  The shell style or gender can be straight plug, angled plug, wall or box mount receptacle, in line or cable receptacle, dummy receptacle, solder or weld mount receptacle, jam nut receptacle, and thru-bulkhead receptacle. Coupling types can be bayonet, threaded, push or pull (ball detent), breech lock, and spring rack or quick connect. Contact size is the designation used to differentiate one contact from another, typically denoted using AWG.

Some common names used for military (MIL-SPEC) connectors rear accessories are endbells, strain-relief clamps, cable clamps, and backshells. Caution must be used when selecting receptacle connector accessories due to the fact that some box mounting receptacles do not have accessory threads, or the threads are of a different size from the plug and may be internal versus external threads. Some military (MIL-SPEC) connectors can include lanyard release. These lanyards can be of various lengths.