Cometic, cylinder base gasket set FR/RR. .010" RCS

Type 'B'. .010" thick RCS (Rubber Coated Steel), an embossed steel core with a .001" thick coating of heat resistant nitrile rubber on both sides. OEM replacement reference 16774-86D, 16789-04.
Type 'A' (early style) and type 'B' (late style) gaskets explained: There are 2 types of cylinder base gaskets for Evolution models available. For convenience sake we'll call them 'type A' (early) and 'type B' (late).
*Type A' gasket was introduced on the 1984 Evolution Big Twin models, and can be used on all of the 84-99 1340cc Evo 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. This can be a problem with silicone beaded base gaskets.
*Type B' gasket was introduced on Evolution XL Sportster models in 1986, and will fit all Evo XL models, but also all 84-99 Evo 1340cc models although the Big Twin cylinder base is a bit larger than the gasket.
The 'type B' is the only gasket type that 'The Factory' supplied from 1986 onwards for both Evo Big Twin and Evo XL Sportster models.
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.