The Pop Up Towing Companion Post Adapter for Curt Double Lock Gooseneck Hitch adapts to older Companion 5th wheel hitches. It converts from Curt Double Lock gooseneck hitch to a square post connecting the Companion 5th Wheel Model 3000.Does not fit the new model 3500 Companion 5th Wheel hitch rated at 20K. For 3500 Companion use item 144754.ONLY fits Curt Double Lock Gooseneck Hitch. Does NOT fit the new model 3500 Companion 5th Wheel Hitch Only fits Curt Double Lock Gooseneck Hitch | Popup Towing Products LLC Pop Up Towing CDL Curt Double Lock Gooseneck Hitch Adapter Post to RVK3000 Companion 5th Wheel Hitch