The AR-STONER Enhanced Stripped AR-15 Billet Upper Receiver is a great choice for your next AR-15 Pistol Caliber Build. Designed specifically for pistol calibers, the upper features an enlarged ejection port engineered for improved reliability and trouble free ejection. Machined from aluminum, this upper is durable and will perform consistently. Sharp lines give your rifle an aesthetically pleasing profile. The flat top A3 design is great for adding your own optics for further customization. Once assembled, this upper fits precisely onto any standard lower receiver. Give your next AR-15 great looks along with great function with the AR-STONER Enhanced Stripped AR-15 Billet Upper Receiver.The AR-STONER Upper Receiver is pre-drilled to accept, a 1/8" x 3/8" alignment pin. Although the alignment pin is not required for installation of this universal upper receiver, a near seamless fit can be achieved when paired with an AR-STONER V2 Free Float Handguard (family #1020691635)...