Julius Mayer JM 35/JM 45 Series Electromechanical Tubular Motor

I received this unit yesterday and when I went to fit it, it wouldn’t fit. The product says it a 35mm motor but fails to say the tub dimension needs to be 38mm for the wheel to fit the roller.I tried to fit it and scratched the unit so wouldn’t be able to return( that was my fault)Looking at other sellers this seems to be the normal description of the unit. Showing the motor size not the tube it fits into when assembledIt was my first so maybe my understanding of how it fitted and what part turned when running didn’t helpThe instructions came in German only so didn’t help me eitherSo for first timer look deeper and find the tube size and not just the motor size in the description