This is a 1 7/8″ hitch ball that has been adapted to work with a stock Rokon tow bar. It has a 5/8″ diameter pilot to fit most tow bars and is secured with a 1/2-20 UNF grade 8 12 point bolt. Some MK4 tow bars have a 1/2″ diameter hole that would need the pilot to be ground off.
I suggest maximum tongue weight not to go over 100 pounds, max. trailer weight of 500 pounds on the level and 300 pounds if any hills are involved. These also require a rigid tow bar that can be shortened to raise the ball height.