Puretane Refined Butane is one of the very few kinds of highly refined bottled butane refills that are made in the United States which means you can trust the plant it was made in was free of any contaminants. It boasts a 99.9998% purity and is among the very best butane you can get. It's laboratory grade n-butane, with only 0.0002% ISO Butane in the mix. The seamless cans have a laminated film of Polyethylene Terephthalate that was chosen because it does not interfere with the N-Butane in any way. Each bottle comes in at 300ML and the can states that it is triple refined, 9x filtered, with zero impurities.