Kaiser Slip-On Lens Cap for Lenses with an Outside Diameter of 42mm (206942) The size of the Kaiser Slip-On Lens Cap reflects the outer diameter of the actual lens and not its thread size. Please measure to the outside diameter of the lens before purchasing any slip-on lens cap Comes with lanyard anchor. Lanyard is sold separately Designed to fit any camera or enlarger lens, binocular, tele-, micro-, or spotting scope lens The cap should fit snuggly but not so tight that it is hard to remove