The Glock 35 Gen 4 in .40 caliber introduces revolutionary design changes to the Glock that dominates the Limited Class of competitive Shooting Sports worldwide. 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, 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 G35 Gen 4 retains the Glock accessory rail for your attachments. 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 plates 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. This pistol does not include the modular sight, just the bracket to mount it on.