All PM discs use a stainless steel outer band made from high grade 420 stainless that will not gall or squeal like lesser quality discs The newest version PM outer bands can be replaced once worn All image discs use a machined aluminum carrier 11.5" discs are bolted to the outer band, 13" discs are attached via floating elements The carrier is perfectly matched to its respective wheel and will have a bolt pattern specific to the front or rear