It fits easily on my Canon ring and my glass has a thread to accommodate the projector, which then becomes a simple extension tube, without having to use the party 31.75. This part can be used also directly on a camera, because it has the same no M42 screws.
The weather unfortunately prevented me from using it under real conditions at the moment, but I intend to remedy this as soon as is possible.
A great product that I recommend without hesitation.