Speed Pro Cast Piston .030 Over H660CP30 offers the performance / dependability of O.E. pistons.FeaturesHigh Quality AluminumControlled Casting Machining for improved reliability, and durabilityUp-tilt ring grooves improve piston to ring sealing provide greater blow-by controlFitsPerformance, Chevrolet, Small Block, 327 Based Engines (4.000 Bore x 3.250 Stroke)