Glock UG3530103MOS: This Glock 35 Gen 4 in 40 S&W caliber introduces revolutionary design changes that dominates the Limited Class of competitive Shooting Sports worldwide. Its modular back strap design lets you instantly customize the grip to adapt to an individual shooter\'s hand size. The surface of the frame employs a scientifically designed, real-world-tested, Gen 4 rough textured technology. Internally, the 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 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. This pistol does not include the modular sight, just the bracket to mount it on.