The Rubber Butt-Pad, 0.30" comes standard with the CTR(R) and MOE(R) Mil-Spec models as well as all STR(R), ACS-L?, ACS? and UBR(R)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.