Te Connectivity Bth3-21-15-1-C-Se.
BACKSHELL, SIZE 21, 90DEG, ALUM ALLOY; Accessory Type:Band Strap Backshell; For Use With:MIL-DTL-38999 Series III & IV Circular Connectors; Connector Shell Size:21; Cable Exit Angle:90°; Connector Body Material:Aluminium Alloy Body