Life Saving Tools BCMA(R) M4 Upper Receiver Assembly (w/ Laser T-Markings) Built to the correct Mil-Specs(Inside Diameter for barrel extension slightly undersized for a tighter fit to the barrel and a more accurate rifle. Please use a heat gun or hair dryer to warm up threaded bore of receiver if barrel extension is too tight.) Precision machined to correct Mil-Specs from 7075 T6 Forgings extension, providing the user with superior strength when dropped or when mortaring malfunction clearance drills. Fully Assembled with forward assist, and ejection port cover Mil-Std 1913 Rail for mounting optics and accessories Machined for use with barrels that use an M4 barrel extension Laser etched T-markings for addressing the remounting of optics Includes Mil-Spec Forward Assist with heat treated tool steel pawl, with press fit and pinned cap Hard Coat Anodized per Mil-A-8625F, Type III, Class2 Dry Film Lube on interior bore per Mil-Specs As with all BCMA(R) products, Made in the U.S.A.