Lightweight, not sure about durability
"I use elecrolytes, and noticed that there's brown rust-like water marks around the base of the bottle threads forming from day 1 . . have never noticed in other s/steel bottles i've used with same electrolyte. Not sure if there's a different plating on the thread section (the inside is brushed steel, but the outer bit has a shinier finish) thats reacting with the salts. No discolouration on the inside of the flask. Do love the lightness of this flask though, and the green colour is fab."