Watch out for Wrong thread castle nuts in BRP Trailer Hitch parts bag!

I bought a BRP Trailer Hitch last week. While installing the long axle bolt, I noticed the thread on the bolt and the castle nut threads did not match. So I went to Home Depot and found a nut that fits for now (Not a castle nut) on the axle bolt. The correct nut is a 12 x 1.25, the castle nut in the parts bag it looks like a 5/16 x 18 thread. The parts bag was factory sealed, so check the threads on the nut and bolt for the axle before you start wrenching.

The nut fits on the bolt, but you cannot turn it!