The Sonnax high clutch hub 28304-SP is an extra strength alternative for 28304. This hub is built to give extra strength in drag racing GM Powerglides where weight is not a consideration. Machined from a high quality medium carbon steel forging, this high clutch hub accepts five friction discs for the added load capacity needed in high horsepower race cars. All splines and thrust surfaces are precision machined to exacting tolerances.