I'd be grateful if anyone with an RB or RZ and waist-level viewfinder would measure the diameter of diopters for it:

http://www.bhphotovideo.com/c/product/33663-REG/Mamiya_213433__1_Diopter_for_Waist.html

I am interested in the glass itself, not the frame that surrounds it.

Thanks very much in advance.

Total diameter of diopter : 45mm.
Diameter of the glass itself that I can see : 36mm .