Precision Reflex's Mark 12 Mod 0 SPR Gen II Upper Receiver is a complete, full-featured tactical upper that's fully assembled and ready to shoot...once you install it on a mil-spec lower receiver. It is fitted with PRI's Gen II Retro Carbon Fiber Forend that replicates the handguard of the U.S. Navy's Mk 12 Mod 0 Special Purpose Rifle. You get a mile-long, uninterrupted expanse of Picatinny top rail extending from the rear of the receiver to the front of the forend. (Maybe we exaggerate slightly - half a mile.) There are also short 3" lengths of Picatinny rail up front in the 3, 6 and 9 o'clock positions. The Mark 12 Mod 0 SPR Gen II Upper Receiver Mfg: Precision Reflex