The Ruger American Rifle Generation II stock features spacers that adjust the rifle&';s length of pull (LOP). The correct LOP enhances comfort and handling and improves accuracy by making shoulder placement and sight alignment quicker and more consistent. The rifle comes with a 13.75&';&'; LOP spacer already installed. The spacers in this kit allow for additional LOP adjustments. The included spacers offer a 12.75&';&'; or 13.25&';&'; LOP when installed. To change spacers, loosen the recoil pad assembly and replace with the appropriate spacer. Only one spacer can be used at a time; spacers cannot be stacked for a longer LOP. Changing spacers is simple and quick with a 3/16&';&'; hex wrench and a 7/16&';&'; socket or wrench. A 1/8&';&'; hex wrench or similar tool is needed to loosen the rear swivel stud (not included).Features : Includes 2 Spacers "Sizes: 12.75" LOP or 13.25" LOP" Compatible with Ruger American Rifle Gen II