[T-Mount] Well made & snug fit. I have 8 FD Lenses from my 35mm film days that I can now repurpose, which were a significant investment. My EOS R is 4 days new (still figuring it out), and at first I thought there was an issue with the mount because the shutter would not release. An email to Tech support, answered within 24 hours, provided the correct settings for the EOS (release shutter without lens). They even provided a screen shot of the menu setting! Great support, great product!

[Canon RF] Got this to adapt my GFX 100s to my Celestron 8SE via an additional T-Mount to SCT and it works great

[0.185 lb] Great build quality and fits perfect.

[T-Mount] This product works great! Solid construction and easy to use with the FD lenses I have.

[0.185 lb] Our old Canon AE-1 Program's lenses are now useable on the new Canon EOS R5 camera. The adapter fits snugly on the lens as well as the camera. I am only an amateur photographer but highly recommend this adapter.

[0.185 lb] Waiting for my back ordered RF lens has allowed me to use this on my R6 and several fd lenses from 24 to 800mm. I have developed some attachment to my old stock lenses and this adapter used with an R6 is a real joy to experience. The lack of glass is a real bonus in image quality. I mounted a fd 800 5.6L to test IBIS, the IBIS does help, I would guess about 2 stops, the lens really magnifies every bump or movement. I shot some good video footage with the combination and setting the stabilization to on during viewing was quite helpful.
I mounted several other lens as well, I was happy with all setups.
Would not hesitate to buy this adapter again. Fits each mount in a snug and secure manner, good product.

[Canon RF] I had a trio of old Canon FD lenses (breech lock) around for years, collecting dust. I decided to make use of them again with my Canon R5 body. This adapter works perfectly once you figure it out, as there are no instructions with it.

The blue ring rotates to allow you to attach the lens to the adapter, then you rotate it to the left (as seen from the back of a Canon camera) to actuate the movement of the aperture blades. Then you focus and meter for the exposure.

About the Arca-style foot: I found this to be awkward when hand-holding the camera. In the comments someone asked if this can be removed, and Fotodiox says it cannot. If found that it can be removed using the proper hex wrench. The foot very securely attached to the adapter, so it took a bit of force to get the bold loose.

On the camera, I found it easiest to use Manual mode, with the ISO setting set to Auto. Also, I had to get into the camera menus and set Release shutter w/o lens to ON or the R5 would refuse to take a photo.

I also have a couple old Nikon lenses around. I may get the Nikon version of this adapter to use those, too!

If you have an old lens you'd like to use with your newer camera, get this adapter. You'll love it.

[0.185 lb] This adapter with Leica 35mm F1.4 lens on Canon R5 body, to focus Manually is fine.

[0.185 lb] I've been using this adapter with my 50mm 1.2L FD lens and the images look flawless on my Canon EOS R

[T-Mount] If you have old -now called V system- Hasselblad/Zeiss lenses around this little gadget will allow you to use them on your mirrorless camera.
You will have to use manual focus and there won't be any stabilization but other than that, they will work well.