These are reproductions of the meter battery cover for the Leicaflex SL and SL2 and are available in black or silver/gray. This is for the bottom of the camera.

Like the standard metal battery covers you must use caution when screwing these into the camera and not cross-thread the threads, but unlike the metal ones, cross-threading these will not damage your camera since they are made from plastic. I tighten them the same way I do my original metal covers by rotating them counter-clockwise till I feel a slight "click". This helps align the threads then tighten as normal, stopping when the resistance is felt