Strike Industries 7-position aluminum receiver extension MIL-SPEC diameter buffer tube allows users to have finer control of their length of pull. The tube's shortest length of pull position is as compact as a fully collapsed M4 carbine butt stock while its longest 7th position stretches the stock to be slightly longer than that of an M16A2 fixed stock. The end plate has a quick detach (QD) build into it for true ambidextrous shooting. It also incorporates easy attachment points on both sides for slings so you can use just about any sling on the market. This kit also comes with a receiver nut for collapsible receiver extension, also referred to as a Castle Nut.