The Extended Rubber Butt-Pad comes standard with the CTR and MOE Commercial-Spec stocks and utilizes a firm rubber that is designed for enhanced shoulder purchase and improved impact/drop mitigation. May also be used with the Mil-Spec models as well as all STR, ACS-L, ACS and UBR stocks for 0.25" increased length-of-pull. NOTE: Not compatible with MOE Fixed Stock. NOTE: This will not provide any extra recoil cushioning as the rubber portion is the same thickness as our standard Rubber Butt-Pad, 0.30". An extra 0.25" of hard polymer is added to the back to provide the extra LOP..