Find 5th Wheels for sale! 5th Wheel RVs, or Fifth-wheel trailers, are designed to be coupled to a special hitch mounted over the rear axle in the bed of a pickup. These trailers can have one, two or three axles and are the largest type of trailer built. Because of their special hitch requirements, fifth-wheel trailers can only be towed by trucks or specialized vehicles prepared for fifth-wheel trailer compatibility. Find your next new or used 5th Wheel RV for sale below.