The RV4XL allows you to pull a fifth wheel with your flatbed truck and gooseneck hitch. The RV4XL is typically used with a flatbed truck with a recessed ball. 11 1/4? height from top of ball to bottom of king pin plate. Longer tube from the coupler to the bottom plate than the Rv4. The RV4XL is designed for use with flatbed pickup trucks. It does not offer enough clearance over the side rails for standard pickup beds.