Ultra-Fab's 35-946510 MegaHitch Coupler Vault Combo Kit is the adjustable, high-density acetate ball system that fits into the coupler the same way as our hitch ball. It's patented design and solid steel construction make it all but impossible for thieves to cut, pry, or disable the lock. Combo kit includes fittings for 2" and 2-5/16" couplers.