The Glock 34 Gen4, in 9x19, introduces revolutionary design changes to the "Tactical/Practical" Glock designed to be the same overall length as the Government Model 1911 pistols. Internally, the Glock dual recoil spring assembly substantially increases the life of the system. The surface of the frame employs the scientifically designed, real-world-tested, Gen 4 rough textured technology. The modular backstrap design lets you instantly customize its grip to adapt to an individual shooter's hand size. The Glock Modular Optic System (MOS) simplifies the mounting of popular optics without costly custom machining of the pistol's slide. MOS has four plate options to comply with the specifications of some of the most trusted optic manufacturers in the industry, and a cover plate when no optic is mounted. MOS gives you the option of adding tall iron sights allowing the optic and the iron sights to co-witness.