I have used these flasks for many years. My wife also uses one. They fit in any pocket including the rear pocket on men's pants. I use them almost every day and have never had one fail. Much better to carry on day hikes than a round bottle. On several -day treks I carry larger bottles in my backpack.
I filled it with water, screwed the cap and seal down tight. I turned it upside down overnight, and it leaked during the night. A flask should not leak when it is not under pressure. The molding around the mouth is poor, and the cap seal does not make up for the poor surface.
As a founding member of The Adventure Flasking Society, I was looking for a durable, high capacity flask for adventures. This one is high capacity, but not so durable. Great thought, but it needs a stronger finish.