The top from the bolt provider groups. The top is definitely the conventional 5.56mm bolt provider group. Detect the bolt, cam pin as well as provider important. On the bottom could be the 9mm SMG bolt team. It truly is a typical FSB and no I'd no problems sighting it https://kameronymwih.blogripley.com/27245002/new-step-by-step-map-for-colt-smg-upper-receiver