Bob is correct. The first time I replaced mine I goofed up by pushing it in too deep and ended up having to replace it. BMW has a tool or gauge to make sure the seal goes in straight and to the right depth.
You can gauge this yourself by paying close attention to the depth of the one you are about to replace. When I worked at the BMW dealership and heard folks asking for the seal, I told them if they were from out of town to buy 2 in case the first did not correct the problem.
For sure, though, make sure you do not scratch the sealing surface or it will leak and that's that. Good luck. It's no big deal if done right.