As everybody knows I have a CV rangefinder lens or three. The lenses come with lovely metal push-on lens caps that work perfectly. Unfortunately they are somewhat spendy for what they are (not as bad as a Leica cap though!). I live in constant fear of either losing or damaging one of them. So, I started looking for a replacement lens cap. The CV screw mount lenses use a short hood that is not threaded at the front. It is ribbed though, so I wondered if a center-pinch cap would work. Looked like it would, but what size? The push-on cap is a 43mm, so obviously it needs to be samller than that, but how much smaller? I picked up a 40.5mm center-pinch cap to test for fit. Well, it works! Hurrah! This particular cap was more expensive than I wanted, so I hit ebay and found some Chinese caps for less than $1.50 each. So now I have cheap caps that are easier to use than the original and it's no big deal if I lose one. And those stock caps can stay in the box in case i ever want to sell a lens.