Fits as a direct replacement upgrade for the standard 55mm manifold. It is a better; stronger and a more heat resistant replacement for the stock plastic (polymer) manifold. Made of T6 heat treated cast aluminum that is CNC machined on outside; but also CNC machined / ported on inside; for the ultimate in high-flow characteristics. Adds 3 to 5 horsepower and up. Especially above 124″ the stock manifold becomes a restrictive part. Complete with a rubber O-ring seal. Easy to install; re-using all stock parts.OEM replacement reference 27300121. Note: For replacement O-ring seal see 974061.
