The .22 caliber Colt M4 Ops is not merely a conversion unit, but a dedicated .22 built from the ground up by German engineers. This handsome rimfire rifle sports an AR-style look and is modeled after the legendary original Colt M4. A "Tactical Rimfire" rifle, the M4 Ops is an upgraded version of the .22 M4 Carbine. Instead of the standard forearm found on the carbine, the Ops has an RIS, or Rail Interface System, that provides tactical railing on four sides allowing for you to mount a variety of available accessories. Additionally, the carry handle that's on the carbine is also replaced by a detachable rear sight making the M4 Ops an ideal optic-ready rimfire rifle. Colt M4 .22 sold by Umarex USA.