Convert-A-Ball have made it easy to find the system that is right for your particular towing needs – and save money! Each set matches two or three sizes of balls with an appropriate shank. Spend less time changing your hook-up and more time towing! The basic Convert-A-Ball® system shank comes to fit in either a 3/4? hole or a 1? hole in your bumper or ball mount. Each shank comes with a lock washer, cotter pin and nut.