PROFESSIONAL PRODUCTS POWER FORCE HARMONIC DAMPER CHEVY BB 454/502 engines (8") 80005 -- 8 in. OD, 13.51 lbs., internal balance; Made from extremely durable nodular iron; Uses a bonding process which adheres the elastomer to the inside of the inertia ring and the outside of the hub, utilizing a strong adhesive along with an improved elastomer to create a much stronger bond; Not made to the original factory diameter; Also works on any displacement big block engine that has a neutral balance rotating assembly; Has a 60 degrees of timing marks and engraved marks every 90 degrees.