This DeeMaxx MAXX Coated Rotor fits a 5 on 4 1/2" bolt pattern idler hub and is a direct replacement for the rotors used in Slip On Disc Brake Kits by DeeMaxx that are rated for 3,500lbs. DeeMaxx developed the MAXX coating as a better, longer lasting layer of protection for their brake components against rust, making this DeeMaxx Rotor a great replacement part for any Saltwater or Fresh Water boat trailer, as well as utility trailers that want a longer-lasting Brake Set up.