The XGBRPX4SC slides over a full-size factory PX4 magazine and seats it in the PX4 Subcompact. In 9mm that is 17 rounds in place of 13, with a grip long enough for the whole hand. The XGRIP carries the Beretta's grip lines down over the longer magazine and closes the step below the frame. Its shape is based on the anthropometrics of the hand and wrist, so the whole hand has a surface to hold. It is cut to seat the magazine at the right depth, and no deeper. Nothing on the pistol is drilled, cut or replaced.