The RM Rail Clamp Module converts your M203 grip fo use with a rail mount. There is no need to slide and position this rail grip. Simply put the RM Rail Clamp where you want it and turn the handle until it tightens on to the rail. The RM Rail Grip attaches to any MIL-S-1913 (Picatinny style) rail. It has a racheting system that holds it anywhere on the rail.