GLK Glock 19 Gen 4 MOS 9mm 4 Inch Barrel Black Finish Fixed Sights 15 Round. MOS (Modular Optics System) platform offers a convenient way to mount reflex sights without costly alterations to a warrantied slide. Includes an Adapter Plate Kit containing 4 adapter plates as well as the tools for the removal and installation for a variety of optics. Optics are not included with the MOS pistols. Fixed sights. Multiple back strap design. Gen4 Rough Textured frame. Dual recoil assembly. Reversible magazine catch. Glock accessory rail. For more info please email us ( Anitasspokentia @ gmail .com ).