EST (Extreme Sealing Technology) gasket kits contain MLS head gaskets, steel Viton coated base gaskets, blue Viton valve stem seals and AFM material Other features include the race style exhaust gasket, that won't fray into the port, and the rocker box base gasket which is made from a single layer of .020" thick embossed Viton coated steel 1550 big bore top end kit EST kits are made for any builder who demands the best and appreciates the long-term value for his/her dollar