The GLOCK 19 Gen 4 MOS 9mm, introduces revolutionary design changes to the pistol that has found worldwide acclaim with security services both private and public. The Modular Back Strap design lets you instantly customize its grip to adapt to an individual shooter’s hand size. The surface of the frame employs the new scientifically designed, real-world-tested, Gen 4 rough textured technology. Internally, the new 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 G19 Gen4 9x19mm retains the GLOCK accessory rail for your attachments. MOS configuration.