Every Whipple Supercharger pulley is made of 6061-T6 billet aluminum and anodizied for wear and envoirnmental protection. Each pulley is engraved with the running diameter size and state-of-the-art light weight pockets to lower recipocating mass as well as a guard feature to help unwanted belt wandering during hard running. Standard finish is hard coated black anodizied. Dimension of each supercharger pulley is based off of the running diameter.