Cometic EST Complete Motor Kit For Harley Twin Cam EST (Extreme Sealing Technology) kits are made for any builder who demands the best and appreciates the long-term value for his/her dollar. Features: For 3.750 Bore .040 MLS Cylinder Head Gasket Kit contains MLS head gaskets, steel Viton coated base gaskets, blue Viton valve stem seals and AFM material Race style exhaust gasket that won't fray into the port Rocker box base gasket, which is made from a single layer of .020 thick embossed Viton coated steel Replaces OEM 17053-99 B Made in the USA