Cometic, builders cylinder base gasket set. 3-1/2" copper

3-1/2" standard bore. With ''type A'' style gaskets. Includes two of each in .005"; .010"; .015" and .020" thickness. These are specialty copper base gaskets for mechanics that want to achieve a specific compression ratio. Type A gasket explained: Type A'' gasket is the early type introduced on the 1984 Evolution Big Twin models; and can be used on all of the 84-99 Evo Big Twin models and will follow the contoures of the cylinder base perfectly. They will fit 86-22 Evo XL; but stick out at the cylinder base. Both type ''A'' and type ''B'' have identical inner bore diameter; oil hole and stud hole locations. Gaskets for front & rear cylinder are identical. Only difference between the ''A'' & ''B'' gaskets is the outside perimeter.