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. A reversible enlarged magazine catch, changeable in seconds, accommodates left or right-handed operators. The surface of the frame employs the scientifically designed, real-world-tested, Gen4 rough textured technology. The modular backstrap design lets you instantly customize its grip to adapt to an individual shooter's hand size. Glock engineers have developed the Glock Modular Optic System (MOS) to simplify mounting of popular optics without costly custom machining of the pistol's slide. The MOS is offered with cover plate when no optic is mounted and four plate options to comply with the specifications of some of the most trusted optic manufacturers in the industry. MOS gives you the option of adding tall iron sights allowing the optic and the iron sights to co-witness.