http://cart.bilsteinus.com/pdfs/E4-WM4-Y650A00.pdf
This guide (second to last page) clearly shows a Bilstein washer going on the top hat of the rear strut... problem is no washer was supplied, just the nut. Washers were supplied for the fronts, but none on the rears. The OEM uses a flange nut on the rears, no washer.
Should I use the supplied nut with no washer? Or the OEM flange nut? I found a few pictures online of the same rears being unboxed and they don't have washers either. Is it supposed to be installed with no washer??