Original rubber plugs A1109870544 are usually ruptured because their surface is deep under door surface. In some cases (on my C124 front adjusting screw) the srew is protruding out so it is impossible to mount original cap without tearing it. My desing moved covering surface on outer side. Be aware that in some instances (second photo) there is so no space enogh. You have to slightly alter my part by grinding / cuting to be capable to assembly it in limited space between outer door sheet and screw head.