Hello I need to replace the felt on my collapsible Summicron f2, because the lens is very hard to push/pull and twist (I twist the lens off my camera if I need to collapse it). Also, this tightness seem to interfere with the focus-action as well, somehow, I am not sure, it may all be in my head Two questions: - How the heck were the Germans able to get the felt in there to begin with? (it's too thick for the inner-tube and the fitting is so tight, the lens is very hard to deal with) - I am thinking about replacing the felt with the light-trap from a 35mm canister (need to check thickness first). Are there other materials more suitable for replacement? If this a non-technical forum where such a question doesn't belong, feel free to delete this post.