I bought an 1 7/8 at TSC with a pretty small shank. Have to check, it was either 3/4 or maybe 5/8. It would have fit my zero turn hitch hole but the ball was then too close to slip my trailer tongue over. I had to buy an ATV adaptor that used a more standard size shank. Of course I have several of those laying around.You might have to be more specific. Of course in the USA, our trailer hitch balls are generally in inches; i.e., 1 7/8", 2", and 2 5/16". Lawn tractors generally are only equipped with a hole in the hitch to use a pin instead of a ball. In fact, with 1 7/8" being our smallest hitch ball, I don't think one is made with a shank small enough for the hole in the hitch. So I reamed the hole and have a 1 7/8" ball on my Toro.