CURT X5 Gooseneck to 5th Wheel Adapter for B& W Hitches, Industry-Standard Base Rails, 20,000 lbs Model 16310CURT X5 Gooseneck to 5th Wheel Adapter for B& W Hitches, Industry Standard Base Rails, 20,000 lbs Model 16310 CURT 5th wheel adapter plates are a fast, dependable way to convert your gooseneck trailer hitch into a set of 5th wheel rails to accept a 5th wheel hitch and switch back again. With gooseneck installation brackets and a gooseneck hitch already mounted, the adapter plate post simply mounts into the gooseneck trailer ball hole using a solid