Polymer with Rubber Grip Area - Mounts on Picatinny rail - Provides natural fighting stance - Rail lug prevents any forward or rearward movement - Skeletonized design reduces weight - Rubberized back for comfortable grip surface - No tools required screw cap storage compartment holds batteries or other small items like firing pins etc - Checkering on finger groove provides added control - Captive thumbnut can't be lost. Provides quick and easy installation without tools to Picatinny rail