That's what I found on Reddit...
This is what I found on McMaster-Carr: https://freeimage.host/i/HDn9Ls2
These are the numbers I got by measuring mine with fair set of digital calipers:
Large X-ring: 7.98mm OD/4.56mm ID/1.87mm thick
Small X-ring: 7.40mm OD/ 4.05mm ID/1.78mm thick
Normalized...