MCS-512422 - Replacement recessed dome pistons for 3-5/8" Big Bore applications. Will fit 84-99 Evolution Big Twin models with S&S SuperStock heads only and 3-5/8" bore cylinders in combination with 4-1/4" (5.375" cylinders; 9.4:1CR); 4-1/2" (5.500" cylinders; 9.8:1CR

Fitment:
84-99 3-5/8" big bore Evo B.T. with S&S SuperStock heads and 4-1/4" (std); 4-1/2" and 4-5/8" stroke flywheels (NU)