[JRTJH]

I think first you'd need to determine the shank (threaded part) length and width, then limit your search for balls that have that size shank. Curt has 2 5/16" balls with shoulders in different heights. More important that the height of the shoulder is the ball weight rating. You can find 2 5/16" balls rated with different weights. Some are only rated to carry 6,000 lbs while some are rated to carry 20,000 lbs, so make sure, if you decide to replace the ball, to get one with the proper size shank and the proper (adequate) weight rating, regardless of how tall the shoulder might be.