This is a complete top end rebuild gasket, seal and O-ring kit for the 1991 through 2003 model year 883cc Sportster engine. Head Gaskets are graphite/carbon on a steel core with a steel Fire Ring. They are a nominal 0.056″ thickness before crush. Rocker Base Gaskets are “SLS” (Single Layer Steel)which is a 1-piece style embossed steel gasket with a thin rubber coating on both sides. A very good seal every time and normally no sealant is needed.