The Glock17 Gen4 9MM MOS (Modular Optic System) introduces new factory design changes to the Glock that runs the Limited Class of competitive Shooting Sports worldwide. Internally the Glock Gen4 dual guide rod assembly substantially increases the life of the system by reducing recoil. An ambidextrous enlarged magazine release can be changeable in seconds, accommodates left or right-handed operators. The surface of the receiver uses the scientifically designed, real-world-tested, Gen4 rough textured technology. The modular backstrap system allows you instantly customize the grip to adapt to an individual shooter's hand size. The G17 Gen4 MOS uses the standard Glock accessory rail for your attachments including lights and lasers. 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. Price does not include the optic. Click here to purchase optics.