Size of 12g plug o-rings on a sydarm?

[afultz075]

On my sydarm, one of the two o-rings on the outside of the plug is looking a little worn. These almost look like they are tank o-rings. Are they tank o-rings or another size?

[ThePixelGuru]

No idea, but o-rings that look the same tend to be the same. Try it, at worst you lose a CO2 cartridge and maybe an o-ring.