I'm sure that in the past I have seen people post what various size o-rings flashlights need. If they see this, maybe they can repost that info for us. I, too, wouldn't mind getting a couple if I could find the right size, especially glow in the dark ones. I have found that with both my G2 and my 6P that the LED drop ins I have in them are slightly longer than the incan P60 they came with. As a result, there are gaps where there didn't use to be, and I think it would be kind of cool to fill them with GITD o-rings.