If you look close at the M.O.M. pics, the red ring is painted on, but the black rings are some sort of material that looks to be glued in place. Can't make out exactly what type of material, but it has somewhat of a texture to it, so it may even be something like cloth!
I just got some metal ones a couple months back, but haven't mounted them yet. Gotta finish painting the new knees first.
