NO REAR SIGHT INCLUDED WOLF A1 T91 AR15 .223/5.56 Gas Piston Upper Receiver with 12.5" Barrel, for SBR (short Barrel Rifle) Builds. Wolf Performance Arms offers shooters this fantastic and reliable AR-15 piston driven barreled upper platform. The WOLF A1 upper features a short stroke piston system, unsurpassed durability and reliability for functioning parts and action while confidently maintaining performance under adverse weather and climatic conditions, the Wolf T91 strives to be the finest and most reliable AR-15 Rifle piston driven barreled upper produced in the world. Additionally, the uppers have amazing ergonomics for both comfort and tactical applications, many of us here at the shop found it to be extremely comfortable to shoot and maneuver with. The WOLF A1 upper is the premier choice when it comes to home defense, Sport shooting, hunting, and tactical applications.