Thinking of turning that stripped lower into an AR-15 pistol? You'll need the proper receiver extension. This one from Bravo Company is a perfect choice. It will work with a carbine buffer and spring, and is machined from 7075-T6 aluminum, hard coat anodized in black. The outside diameter is 1.2", just the right size to fit an ATF compliant SIG SB15 pistol stabilizing brace for the ultimate personal defense weapon (PDW).

Features and Specifications:
Manufacturer Number: BCM-PISTOL-RE-KIT
Works with carbine buffer and springs
7075-T6 aircraft grade aluminum
Mil-spec hard coat type III anodized
Outside diameter 1.2"
Black

Includes:
BCM® GUNFIGHTER™ QD Receiver End Plate
Lock Nut (Castle) M4
Action Spring, Carbine
Buffer Assembly, Carbine This kit is compatible with your ATF compliant SigTac SB15 type pistol stabilizing brace.