The Pop Up Towing Companion Post Adapter for Flip-Over Hitch adapts to newer model 3500 Companion 5th wheel hitches. It converts from a round hole to a square post for mounting accessories. Does not fit the older model 3000 Companion 5th Wheel hitch rated under 20K. For 3000 Companion use item 144751.ONLY fits Flip-Over Hitches made by Pop Up. This product will not work with the 317 or 318 models. Does NOT fit older model 3000 Companion 5th Wheel Hitches under 20K Only fits Flip-Over Hitches made by Pop Up Will not work with the 317 or 318 models | Popup Towing Products LLC Pop Up Towing FLC-1 Adapter to RVK3500 Fits PopUp Flip Over System Only