I remixed this to use with the lenses cut out of a pair of my cheap cardboard Solar Eclipse glasses. I also resized them to fit snugly on my binoculars that have an outside diameter of roughly 61mm.

Use a pencil/pen to trace the inside of the larger ring onto the cardboard glasses you are sacrificing for this project, then cut along your line. I used some tape to help hold the lenses in before snapping in the inner ring, but this probably is not necessary.

Good luck and enjoy the great American eclipse of 2017!