I'm searching to buy a (couple of) rubber ring(s) to replace the original sealing at the base of my Gaoersi 8x focusing loupe, which I lost the other day. The ring is a protection against scratches to the ground glass of the camera, caused by the sharp-edged inner ring of the loupe's metal casing. There is space to insert the respective ring. It seems that a 40mm diameter ring is needed, however, I'm not sure as to the required thickness. Could anybody please have a brief look at their own loupe and help me out with this missing piece of information? I would estimate it to be in the 2.4 / 2.5 mm range, but I'm just not sure.
Thank you very much for taking the time!
Norbert