The answer to the rust was titanium. Titanium grows its own oxide layer and then stops caring.
What we did not know was that the material picks the shape.
The oblong can could not be made in titanium. Not by any factory we asked. The rims, the seams, the flat sides: all of it depended on forming steel in ways titanium will not go.
So the flask became one body. No seam, no rim, no lip. One form, with a mouth sized for pouring and nowhere for water to sit.
People had already ordered the can. There was no can anymore.
We emailed all of them and told them what we had changed and why. About half opened it. Not one person who opened it told us it was worse.
That is the entire reason it exists in this shape.
the list goes first.
Every entry goes to the list by email. When the next flasks go on sale, the list can buy 24 hours before the public. No discounts. No codes.