The Rubber Butt-Pad 0.30" comes standard with the CTR and MOE Mil-Spec Carbine models as well as all STR, ACS-L, ACS and UBR stocks and utilizes a firm rubber that is designed for enhanced shoulder purchase and improved impact/drop mitigation. May also be installed on Commercial-Spec MOE/CTR stocks, but may prohibit use of fully collapsed position. All mounting hardware included. RSR -