Description
KAC-Knight’s Armament SR-25 Ejection Port Dust Cover Retaining Spring (20397)
Other parts required for a complete assembly:
https://www.operationparts.com/kac-knights-armament-sr-25-ejection-port-cover-assembly-extended/
https://www.operationparts.com/kac-knights-armament-sr-25-ejection-port-cover-pin/
https://www.operationparts.com/kac-knights-armament-sr-25-ejection-port-cover-spring/