The conversion is 100% reversible. Unlike other kits on the market, with mine you don't need to drill a hole in your lens! Don't do that!
You will still need to adjust the infinity focus of the lens after you put the adapter on.
*Wide angle Rokkor lenses like the 24mm can often be infinity focus adjusted, but still should not be used with full-frame DSLR Canon cameras.
This is because the lens' rear element extends too far back into the camera and will hit the mirror during shooting.
This issue won't happen with with EF to RF adapters, drop in filters, and speed boosters. The issue is only on full frame DSLR cameras so far as I can tell.
No re-housing company or conversion kit can fix this issue, it's just a product of the way the glass is arranged.
On my canon 6D, any lens wider than 80mm (ish) can't be used to take a picture with the mirror actuating on the camera. Video still works though if you lock the mirror.
I love using my Rokkor MCIII 24mm SI on with a drop in filter adapter on a mirrorless camera. So far as I know all the lenses which can be infinity focus adjusted will work great on any RF to EF adapter in spite of the rear element issue on full frame DSLR mirrored cameras.
I 3D print these in house with heat and UV resistant ASA plastic. They are safe to leave in a hot car on a sunny day.
Two conversion kits are included with every order to make sure you have spare parts, or you can just convert two lenses.
I'm proud to say that they fit the lenses very nicely and they fit my Canon 6D just right.
My EF to RF adapters also work great with these. They mount basically just as well as a factory made lens mount. I think making them in house lets me control the quality well. I spare no expense and use dissolving supports to achieve great dimension accuracy on my kits. I think mine are much better than the ones available on shapeways.
My kit comes with a pop in piece that will allows you to glue on an aftermarket EF chip if you'd like to do that.
This adapter works well on both MD and MC lenses.
*This is the only safe conversion kit for MC III lenses that I'm aware of. If you are not converting an MC III lens (rubber grip lenses) then feel free to use the MD version on your lens without the plastic spacer ring.
-The MC III lenses have a .5mm step down where the camera meets the lens. That step can cause full frame cameras to collide their mirror with the silver part of the SR mount. This is the worst type of collision. Hitting the rear element is normally harmless but hitting the silver flange is not because the mirror gets stuck against the mount.
My mount uses a thin plastic spacer to protect your camera and ensure that MC III lenses will never destroy any camera!
The spacer also protects the lens and camera from general ware. So far as I know I'm the only person making safe ones like this.