This is just a heads up and question for all of you. Twice now after using s certain DIY juice (7% TFA spearmint + 1 drop sweetner per 10 ML + 50/50 PG/VG 0 nic) The o-ring inside the cap of the REO bottle has swelled up so badly it would no longer fit and went totally vertical up into the cone of the cap. Why twice? Because the first time I wasn't sure which flavor had done it. Now I know it is the the TFA Spearmint. SO heads up on that flavor not playing nice with our beloved REOs. Now for the question Does anyone happen to know what size that o-ring is? If I am going to be burning through them when I run into a juice that doesn't play nice I might not always be able to buy a replacement from Rob fast enough.