The Canon EOS wide T2 adapter has a M48 thread that is ideal for full frame cameras
The standard T2 ring uses a M42 thread that is suitable only for Canon Cameras with APS sensor. Full frame sensors have a diagonal of 43.3mm which which is wider than the 42mm thread of standard T2 ring. Using a T2 ring on full frame cameras will cause vignetting.
This adapter suit the majority of Canon EOS cameras.
It is not compatible with Canon cameras with M mount or RF mount.