RV Bumper Adapter for Hitch Racks - This adapter attaches to your 4 to 4-1/2 inch RV bumper with U-bolts, giving you a 2 inch receiver opening that works great with hitch mounted bike racks and cargo carriers. Its solid steel construction and anti-rattle technology provide a strong, stable base for the bike rack or other accessory. Designed exclusively for 4 inch to 4-1/2 inch continuous-welded steel bumpers, this adapter is not compatible with aluminum or spot-welded steel bumpers. (Do Not Use For Towing.) Never exceed the bumpers stated capacities. Distance from the center of hitch pin hole to end of receiver is 3 inch.