OP/TECH USA Lens Mount Cap - Leica M Double, Black (1101231)...

If youre carrying around enough lenses that you need this double cap, then at least one of those lenses will be wide angle (eg 35mm or 28mm). Sorry, those lenses will not fit in this cap. Its too shallow. Its significantly shallower than the standard M mount rear cap. My 50/2 and 90/2.5 fit in it but nobody caries three lenses

Ive been using these caps for maybe decades. On Nikon, Canon and now Leica M. I had a Fuji in there for a while, didnt know these existed for it, so I made my own. I love these for packing shorter lenses in a taller bag. Very useful for travel when I might pack 8 or more lenses, but also very practical in a daily bag of limited square mm and taller depth. Im here buying a 2nd Leica M double back (now that I have 4 Leica lenses) but Ill pick up a 4th EF double back to better store my collection of Zeiss EF lenses. (I dont see an RF mount available yet but I only have 3- RF Lenses, and theyre larger zooms.)

This cap did not fit any of my M lenses. They would not turn or screw into the cap. I like Optech products in general, but this one is junk. Very poor quality control.

Nice idea - being able to stack a pair of lenses back-to-back. The Leica M version is much wider in diameter than needed, significantly wider (65mm) than a typical M lenses or a Leica cap (50mm). Rubber O ring is nice for sealing the lens against the cap but does not need all that width. The alignment mark is a little hard to notice - a Leica-style "dot" or dimple would be better and a dab of contrasting paint would have been trivial to apply to a better design..

So, I was minding my own business, hopping rock to rock with my camera bag over a river, and came to a dead end. The high water made that path impassible without getting wet. So I backtracked. On the last big hope, I passed my balance test perfectly, nailing the landing... but tragically, failed my physics test, not noting that the combination of forward momentum and slime-induced low friction surfaces would keep me going... into the drink. The result was a killed Olympus Pen-F camera -- not even weatherproof. But tragically, also an Olympus M.Zuiko 12-40mm f/2.8 PRO lens, which was weatherproof and in the bag, with an end cap on. My conclusions: the standard end caps don't provide a good enough seal. And so I found these. They work very well in sealing against your lens. I'd advise, as with all water resistant things, to occasionally add a smear of silicon grease to the O-ring, but otherwise, a good deal. So now, on to what I don't like about these. I ordered several caps, first a pair of the single and dual caps, then, once having proven them worthy, I ordered three more of each. I opened 'em up, brought them to my photo gear corner, and gradually started using them. It was only when I realized that I had trouble getting one off that I saw the problem: out of eight caps I ordered, two were sent for the wrong camera. And it was months before I discovered that, indeed, I had a single cap for a Fujifilm X-Mount and a dual cap for a Sony E-Mount. I had ordered only M43 mount caps. So while I can recommend the caps themselves, they seem to be packaged and shipped by crazed orangutans. Should you order any of these, do inspect them very, very carefully before assuming you have the correct cap. Don't trust the packaging, either, as both of mine indicated the correct cap on the packaging. But there's a little white sticker in each cap that reveals its true, and possibly alien, nature.