With the help of this lens adapter you can attach a Canon EOS lens to ZWO ASI (or other) cameras with flange focal distance of 12.5 or 17.5mm when used without a filter wheel.
This new EOS-T2 adapter consists of three parts. The EOS-T2 adapter itself consists of two parts, but usually used as a single unit, and then there is an additional T2-extender of 5mm length.
Currently, using the adapter with or without the 5mm extension makes it suitable for all ASI cameras.
This new type is NOT adjustable. This EOS-T2 adapter supports Canon EF lenses only.
Optical length: 30.5mm (inc 5mm removable extension) (this is how you would use it with a ZWO camera that has 12.5mm focal flange distance, to achieve a total of 43mm back focal distance)
Optical length without extension: 25.5mm (this is how you would use it with a ZWO camera that has 17.5mm focal flange distance, to achieve a total of 43mm back focal distance)
(we guess that with this you can achieve 43mm instead of the usual 44mm of a Canon camera, because if you insert a thick filter, that would also add a bit to the back focus, so this way you will still not run out of distance to be able to focus at infinity)