Designed to simplify and reduce the time required to prepare crankcases and cylinder heads for S&S Cycle Sidewinder big bore kit installations Machined cast iron with precision ground working surfaces This boring plate kit has panhead and shovelhead head bolt patterns in one end. The other end is machined with the cylinder base patterns of 1936-99 Big Twin engines, and 1986-2003 Harley-Davidson Sportster models. Spacers are available for Evolution engines which allow the cases to be bored without removing the cylinder studs. Spacers are not included in this kit.