Shock/Strut Replacement Questions..

Hey all,

I'm just about to replace the shocks and struts on my baby with some nice bilsteins I got. I've been told that when replacing the rears there are some parts that I should not re-use. Can anyone give me a list of what I should go purchase and replace while I'm in there? I kind of figured the upper mounts were a given :)

Thanks!

Jeremy
99 M3 Cabrio (Techno Violet)