CMMG Inc Upper Completion Kit AR-15 Forward Assist Plunger/Spring/Roll Pin Ejection Port Cover/Hinge Pin/Cover Spring/Hinge Pin C-Clip Black. 56x45mm NATO Gun Model: AR-15 Included Accessories: Hinge Pin C-Clip Ejection Port Cover Hinge Pin Forward Assist Roll Pin Forward Assist Plunger Ejection Port Cover Spring Ejection Port Cover Forward Assist Spring Package Contents: CMMG Inc AR-15 Upper Completion Kit What firearm models does the manufacturer say CMMG Inc AR-15 Upper Completion Kit is compatible with? The manufacturer suggests that CMMG Inc AR-15 Upper Completion Kit is compatible with AR-15CMMG Inc 55AFEF2: Upper Completion Kit AR-15 Forward Assist Plunger/Spring/Roll Pin Ejection Port Cover/Hinge Pin/Cover Spring/Hinge Pin C-Clip Black