The Aero Precision M4E1 Complete Lower Receiver with SB Tactical Stabilizing Brace is the perfect starting place for your AR pistol build. This complete lower features an M4E1 Lower and is upgraded to include an SB Tactical SBA3 Stabilizing Brace. The SBA3 is an adjustable ATF Compliant Pistol Stabilizing Brace that provides integral QD sling sockets and increased stability for your AR Pistol. Save when you buy this Complete Lower Receiver and let our specialists do the installation for you!Includes: M4E1 Lower Receiver A2 Grip SBA3 Brace Lower Parts Kit Carbine Receiver Extension AR15 Carbine Buffer and Spring These parts are installed