Interesting, any reason other than being able to put direct flame under them than sticking with nalgene?
That's the main reason I tried it out. I have water purification tabs in my EDC but I thought it might be nice to have the option to boil water or make a hot drink in the bottle. It lets me avoid having to carry a separate metal pot/cup. I have some of
these pouches in my EDC bag for holding more water.
The smooth 304 stainless is about as inert as you can get, too.