VISM Vertical Grip for Picatinny and Weaver Features Tool-less design for mounting on rails Twist the bottom knurled knob until the recoil detent is flush below the mount Slide the vertical grip onto the rail Use side witness holes to align with a rail cross slot and tighten the knurled knob until the detent locks the grip to the rail. Grooved vertical grip surface for a secure grip Overall height 4.5″ H, 3.75″ H grip surface Vertical grip is made from black polymer plastic Vertical Grip is not designed for Pump Shotguns Specifications