Compatible with standard 50mm hook ball: : Our plastic hook ball cover is compatible with any 50mm diameter hook ball. It fits all tow balls, including gooseneck or bolt-on tow bars. Also suitable for all types of vehicles, commercial vehicles, trailers, cars, etc. Anti-mud: : When the ball joint is not in use, you can wear our tow cap to prevent the ball joint from sticking in the mud, keep the ball joint clean, reduce dust and sand, and extend the life of the ball head. The life of the tow ball and tow hitch. Chrome and rust-proof surface: : The pull up ball is made of high quality ABS material, which is high quality and durable, and can be used for a long time. The surface is chrome plated to prevent rust and scratches. Easy to install: : our trailer dome is designed for maximum comfort, easy to install, no additional tools required. Simply push the tow ball cover into your car. Portable and easy to carry: : The tow ball cover can protect your tow ball when not in use, and it looks good. Small and light, easy to carry and store.