OEM hitch only... unless you are referring to the Reese part that is is square tube with the ball at the end that fits into the square hole, the hole being part of the car's rear bumper assembly...
that hole thingy should bear Westfalia or BMW sticker - westfalia is the manufacturer of that hitch thingy... If you look around the forum, you will see that the factory hitch is a substantial equipment that is substituting some of the original bumper assemblies in the key locations - something, that an aftermarket hitch can not accomplish