Genuine BMW part 71 60 1 090 370: Collar nut. The number stamped on the part is 71601090370; BMW's catalog files it under the short number 1090370. You will find it on our Tools shelf, under Other Equipment Parts parts.
It fits the E36 sedan, coupe and convertible (318i, 320i, 323i, 325i and 328i, 1992–1999), with the M40, M42, M43, M44, M50 or M52 engines — and the European-market versions.
BMW draws it on the Trailer Hitch/Electr.Attaching Parts (71_0112) diagram. BMW's catalog calls for four of these at each place it is fitted. It weighs about 10 g (under 0.1 lb). It also comes in BMW kit Scdel. of tow.hitch+detach.ball head (1094390).
We have not had one on the shelf yet. Request it and we will tell you when one comes off a car.