Bulldog 1289050300 Gooseneck Coupler - Inner Tube Only 4 inch diameter inner tube only - short configuration Resists theft with integrated feature to allow pad-locking the coupler to the ball (lock not included) Provides continuous tight ball fit with ever-increasing cam tightening locking mechanism - 2-5/16 inch ball socket. 30,000 lb gross trailer weight rating. Lengthens life of locking mechanism with oil-impregnated bushing and grease fittings on critical moving parts Read product description below for more detailed information.