D38999 Series I/II Backshell — Straight, Direct Coupling, Shell 10

Specifications

Part Number Decode

The /29 is the Series I and II counterpart of the /21, and the key difference is coupling behaviour. Direct coupling means the backshell body itself is turned to engage the accessory thread, so the cable must be dressed afterwards; spin coupling on the /21 turns only the nut so the bundle is never rotated. Series I and II 38999 connectors use a bayonet coupling and lower accessory torque, which is why direct coupling is acceptable there.

Interchangeable with any QPL M85049/29 backshell of the same shell size and finish. Grouped for MIL-DTL-38999 Series I and II and equivalent European specifications.

Cross-Brand Compatibility

The practical rule is to match the backshell family to the connector series: /29 for Series I and II bayonet connectors, /21 for Series III and IV threaded connectors. Fitting the wrong family usually still threads on but leaves the wrong coupling behaviour and, in the case of direct coupling on a Series III connector, can unscrew the connector when the cable is pulled. Airoadcon supplies both families with the finish menu documented per slash sheet.