The Allstar Performance SB Chevy Aluminum Crank Hub was design specifically with circle track racers in mind. This lightweight aluminum hub is significantly lighter than traditional harmonic balancers, and dramatically reduces rotating weight for quicker acceleration at the corner exit. It weighs just 1 pound! The Crank Hub has engraved timing marks at 0° and from 30°-42°. It is 4-3/8" in diameter, and features three 3/8"-16 pulley threads. As this is a hub, and not a harmonic damper, it is designed for internally balanced engines only and must be balanced with rotating assembly.