I see what you mean Lol. I never ordered from FT cause they take Foreveeeeer to ship stuff. And honestly I wouldn't know how to answer that question cause I never used the metal tank long enough to tell between the two. I Don't even know how much I filled I'd say at least half way and ran it down to a dry hit and changed to the large M tank. Good question tho I wonder as well lol. If they made a metal tank with a window at the bottom that'd be nice.