The top from the bolt carrier groups. The top would be the typical 5.56mm bolt carrier group. Recognize the bolt, cam pin and the provider critical. On the bottom will be the 9mm SMG bolt team. The modified near selection aperture (fifty meters) for your Colt 9mm SMG is engaged. https://colt-9mm-upper52851.blogdun.com/27064407/the-colt-10-5-inch-9mm-smg-upper-receiver-assembly-diaries