O-rings is where I got mine. 12mm x 1.5mm seems to be a better fit for 16. 18 is 10mm x 1.5mm. I don't think there's an issue with 18, it might just be condensation in the chamber.
I ordered a 5pk of glass from FT. A day later, they have a 10pk for a buck more and it comes with a case![]()
I want the case...