Your Trailer hitch ball will fit on to the ball mount. There are several styles and sizes of Hitch balls available and each item being towed may have a different requirement. Please note, it is very important to pay attention to the towball weight rating and not exceed this. Equal to or larger(more weight) then what you need are always the best rule of thumb.
In General Terms:Class II Ball Mounts - 3/4" diameter ball shank
Class III ball mounts - 1" diameter ball shank
Class IV & V Ball Mounts - 1-1/4" diameter ball shank