The G40 Gen4 in the MOS Configuration is chambered in 10mm and combines a full 6-inch barrel for an improved velocity with a magazine capacity of 15 rounds. The G40 Gen4 in MOS configuration is a powerful yet easily carried pistol; perfect for the outdoorsperson" hunter and sport shooter. It is designed to give the handgun hunter the ultimate choice in semi-automatic gaming pistol and has proven to be more than capable of taking down game such as Whitetail Deer" Russian Boar and even Feral Hogs. 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.