''Type A'' gasket. 3-5/8" big bore copper gasket. Type A gasket explained: The ''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.