[0.34 lb] The M-42 thread is not directly machined into the barrel. It is a seperate piece, so I was able to remove it, then remove the pin-depresser-ring, and then reinstall the M-42 piece (plus a shim).


This means I can deploy this item either with or without the pin depresser. (If this means nothing to you, then buy the cheaper version.)

[Aluminum] I never though I'd ever get to use my 50 year old Rikenon lens again, but now I can. Fits both the camera body and the lens firmly and allows full focus to infinity. Noe I can play around with bokeh effects using my f 1.4 50 mm.

[0.34 lb] I love it, not surprised in the slightest that it fits perfectly.

[0.34 lb] Backfocus dimension is eerily perfect, seems to reach infinity exactly at the infinity stop on the lens. Slightly worrying: what if it doesn't quite reach infinity? On the other hand, why argue with perfection?
This appears to be a single piece of metal, finished inside and out with some matte black anodizing or paint. Slightly worrying: what if it wears off and leaves black dust inside the camera? Chrome plated wearing surfaces would be more reassuring. But again, no actual sign of a problem.
Orientation of the lens when screwed on: quite acceptable, pretty close to centered. Fortunate, since it can't be adjusted.
Price: surprisingly low for something from this premium brand.
So, hey, seems like by far the best option out there for this kind of adapter.

[Aluminum] Works perfectly for my Helios 44-M4 lens on the BMPCC4K camera. Not even any glass elements to worry about getting dusty.

[Aluminum] Very nicely made adapter with proper fit to Leica SL series cameras. I purchased this to connect my SL2-S to an astronomical telescope focuser using a 2 nosepiece. What I learned upon receipt is the difference between M2 (1.0mm thread pitch) and T2 (.75mm thread pitch)... most astronomical fittings are T2 and will not attach properly to M42 without an M2-T2 adapter. These exist but are not easy to find. Fortunately I did source one and the adapter now works perfectly for my intended use.

[0.34 lb] The Novaflex adapter has let me use my wonderful really old Pentax M42 50mm macro lens again, on my Panasonic GF1 and GH2. With the crop factor of 2, the lens becomes a 100 mm in 35mm terms, a very convenient focal length for macro work. The build quality on the adapter is excellent.

[Aluminum] Got this to adapt my collection of Takumar lenses for my new S1H. This adapter feels perfectly sturdy and does what it was designed to do. Extra meaningful because it let me adapt lenses left from my late grandfather. Definitely the adapter to get for Leica L-mount cameras.

[0.34 lb] I bought this to attach my old Russian lens to my GH5 and it seems to work well. I have tried it out in the field yet, but so far so good.