Built to the MIL-DTL-38999 standard (formerly MIL-C-38999) the connectors are used in the following types of application: Series I connectors are used where a quick disconnect coupling system is required for blind mating or other mating-difficult areas; Series II connectors are used where the connector is not subjected to high vibration or damp areas and where space or weight is at a premium due to their lower profile; Series III connectors are suitable for blind mating areas, and provide high-vibration characteristics at elevated temperature and are suitable for damp areas with the proper connector accessories; Series IV connectors are used where a quick disconnect coupling system is required for blind mating or other mating problem areas. 

• I series: bayonet connection, anti oblique insertion, 1-128 contacts
• II series: bayonet connection, short shell, non diagonal insertion, 1-128 contacts
• III series: three head self-locking threaded connection, anti oblique insertion, 1-128 contacts
• IV series: Push pull quick lock, anti oblique insertion, 1-128 contacts

Typical applications for MIL-DTL-38999 connectors and accessories include aerospace and military systems.