This is the nice black metal slip on front cap for the 35mm and 50mm Summicron and possibly others. It has the nice black exterior finish and a cool red velvet fabric lining around the interior edge. The inside diameter measures ~42mm.
It is in excellent condition with light wear. There is a pinprick dent near "L" in Leica but it is very small and minor. There are no major dents or significant wear. The cap works perfectly.