Omega Supercharger o-ring

[Matt247365]

Anyone know the exact size/type of this o-ring?
Looks like ID is 14mm.
Tried a 14mm ID from the hardware store but it just squeezes out as if the durometer is too soft.
Manual diagram shows it but doesn't list it's attributes.

Thanks, Guys!

https://www.airgunsofarizona.com/content/admin/plugins/custom_fields/files/1173839153Manual%20-%20Omega%20Super%20Charger%202017.pdf

 

[Gerry52]

Is the old one missing? Do you have a caliper? EVERY airgunner shalt have thou a caliper! It's one of the 10 commandments (of airgunning).