Talking about size, crystal measurement is made in means of length and without the top Octagon.

Standard sizes are:

        1.5" (38 mm)

        2" (50 mm)

        2.5" (63 mm)

        3" (76mm)

   .    3.5" (89 mm)

   .    4" (101 mm)
 

To Print the Ruler, push on the below image

Note: you have to select Actual size when Print Window Pop Up