So my biggest hesitation in getting a Hassy 40mm FLE was the odd-ball filters size of drop in 93mm. There are *very* limited options out there and what there is to be had is very expensive even used, almost always over $200. In comparison, there are tons of 95mm filters out there and often for not a lot of money. I primarily use 3 filters in my black and white photography on wides, a polarizer is not one of them, too uneven in the sky. The three I do use are an R72 for infrared, 10 stop ND filter and a 25 red. The red and yellow is available as 93 drop in but the other two are not. So I took a really good look at the lens when I got it, played around with finding the cut off when a filter ring would show in the frame at F22, closest focus, etc. and came up with a couple of ideas. Here is what I settled on: The first item I ordered is this 93mm to 95mm adapter ring, made specially for the 40mm FLE and 350mm CF. It was shipped fast and the machining is perfect, no burrs. Next on the list were the filters themselves. The red was easy, I found a brand new in the box B+W for $80. I then found a 9 stop ND filter for $99 and a 720nm IR filter for $57.22, all three filters threaded perfectly onto the adapter. The ND filter was exactly 9 stops and actually had better color correction than the two 10 stop B+W filters I have which tend to trend warm, not a big deal for black and white work. The 720nm IR filter was also perfect, tested with both Rollei IR400 and Efke IR820. Both filters are made well enough and have very even coatings, sharpness on par with B+W glass. In my opinion, this is the way to go for filtering the 40mm FLE, better than adapting the built in shade removed 86mm to 95mm version because the standard lens cap fits over the 93mm to 95mm adapter perfectly. And of course, far better than the silly 93mm version filters. As for shading the lens, some will argue that this can get in the way of using shades like the 6093T and the like, but I use things like ball caps, my hands with black glove liners on to do that anyway and usually shoot in light that it simply does not matter as much. So for the average price of one 93mm drop in filter, I got the three filters I need the most and the adapter ring. Hopefully someone else can try this out too and enjoy a cost effective way to filter the 40mm FLE.