Erm i thought that Luxfer was the make of bottle... not the material - which is an alloy bottle with a fibre wrap... Therefore they should be ok with Co2.Erm HPA tanks arent designed to hold Co2, due to the effects of it expanding and contracting of the liquid. And if i remember luxfer is like some kind of fibre. And they are severly affected by liquid co2, causing a serious hazard.