Jason,
If you are referring to the 2 rubber bumpers (stops), these are a bit hard to install when the bumpers are new. Seems the rubber is larger than the housing, and the rubber fights against you...
To install mine, I ended up sanding a couple of mm off of the rubber (sand only to the depth of the metal housing whichs holds the bumper).
Using gloves to get a better grip, as well as some silicon spray lube on the rubber section being insterted, I turned the bumbers while applying some downward force. Sort of screwed them in...
Very tight fit, but they went in and have held up well!
Good luck!
Bob
bpossel (Memphis, TN.)
'71 280SL / '97 E320