The M68 sensor tilt plate has been developed by ZWO and specially made the M68 off axis guider. It allow to adjust the tilt of the ASI 6200 camera.
It has an optical thickness of 5mm and a female M68 thread.
I ordered this product to allow a greater clear aperture for using my ASI6200MM. Whilst it is exactly what is claims to be, it isn't as well finished as the M54 version in that it doesn't have the foam rubber sponge around the base to protect it from stray light.
There is an argument to made as to whether or not it even could given the limited real-estate on the plate itself, but it's a less than perfect design from the same company that makes the entire unit - so there is no-one to blame but themselves.
NONE of this is of course the fault of Testar, great folks!