Part 1 - Minolta MD to Sony NEX adapter

Technically, it slightly overshoots infinity but the issue is easily corrected by dialing back the focus ring just a tad --- Not exact but clearly better than not-at-all.

Although very light due to extensive aluminum usage, the build quality and fit-and-finish of the adapter is superb. Connections on the lens and camera mount sides are tight and precise --- absolutely, zero slop. The top of the lens release button is flattened making the lens removal process very easy and comfortable.

Other notes:
- There are no electrical connections so focus and zoom must be done manually on the lens itself
- When mounting the lens, turn the adapter clockwise till you hear a "click"
- Tested with a Minolta 85mm f/1.7 Rokkor-X MD lens mounted to a Sony a6000 camera

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Part 2 - Nikon Ai to Sony NEX adapter

Edit: Based on my positive experience with the Minolta MD adapter, I also purchased the Nikon Ai adapter later.

As with the Minolta MD adapter, the Nikon Ai version focuses beyond infinity a tiny bit. Fortunately, the same solution applies - dial back the focus ring and the horizon will become crystal clear. The build quality is impeccable and the finish is smooth and clean of burrs or machine marks. Connections on both sides are taut and precise with zero play.

Additional notes for Nikon Ai adapter:
- No electrical connections present so focus and zoom must be done manually on the lens.
- Unlike the Minolta MD adapter, mounting the lens for Nikon adapter requires a counter-clockwise turn until you hear the "click" of the locking mechanism
- Tested with a Nikon Micro Nikkor 55m f/2.8 Ai-S MF lens mounted to a Sony a6000 camera

I have a few other adapters and they are all OK but this one is the best. The Fotga is fits fine and is quite functional but the K&F seems a bit more solid. But what really sets the K&F apart is its larger release button which is easier and more comfortable to use. Honestly, it kind of hurts my finger to push the release on the Fotga and my Fotodiox. I'll occasionally still use the Fotodiox when I need an adapter with tripod mount but the K&F is my fav. I recently picked up a Leica lens and needed and adapter. No question, I ordered the K&F.
Note on the picture: I'm holding the FOTGA and the K&F is on the camera. You can compare the release buttons.

Super well built, using it on a a7s. Proper infinity on all lenses used so far. Tight fit on both sides.

Works great lens fits great on the adapter and the adapter fits great on the body. No wiggling

Very precise Contax -> Sony E adapter with good workmanship.

Keeps focus even with parfocal zooms - important for video users.

Unassuming design - only the release button could be a little more high-quality - but it does exactly what it's supposed to. A small transport case is also included.

So you get solid performance for a fair price!

I bought an adapter for Sony M42. The adapter fits pretty well and is very sturdy. I used it for a while with a 50mm Super Takumar and I noticed that the focus never reached infinity so the pull is not very precise (at least for the lens I use). Fortunately, by loosening the three small screws that hold the various pieces of the adapter together I discovered that inside there is a black plastic ring that acts as a spacer. After removing the ring I was able to focus up to infinity but unfortunately it also went beyond that. So I printed in PLA several adapter rings with different thicknesses ranging from 0.6mm to 1.2mm. Problem solved and perfect pull.

Fits securely and does an excellent job as an adapter for my Sony alpha.

I haven't tried any other model but this does the job well at a fair price.
Easy to connect, feels sturdy, looks good, came in a nice box.

Photo taken with a worn Minolta MD Rokkor 50mm 1.4 on a A7RIII.

Edit -- it does leak a bit of light (test with a 30 sec exposure with front cap on) but to me this gives a very interesting effect - see photo, it doesn't spoil the image but gives it a luminous effect, like the light is bleeding out of the photo.

Please note: Their updated model, with the copper ring matching that of the camera doesn't leak light (same test). Keep this in mind if you don't like that, as it's only a few pounds more. (I have tested that updated model on a M42 model as well, no light leak.

Fast delivery, very good build quality And an Excellent value for money .
Really happy with it .
I highly recommend these to anyone using vitnage lenses

Excellent value for money. Very nicely made for the price, neither loose or tight on lens or camera body. Aperture selection is easy and well defined. Works perfectly.
Just remember there’s is no electrical connection so no AF, AE, VR or metadata. Doesn’t matter just make sure you can work manually.