Unfortunately, it doesn't work because the lock falls apart almost every time it's used.
The problem is this:
The plate that closes the thermos flask at the bottom of the cap and prevents the bottle from leaking has a rod at the top that is guided by a spring. At the top of the spring is a small plastic cap that rests on the spring and is clamped onto the rod of the closure plate. This plastic cap always comes off, causing the cap to disappear into the tea and the thermos flask to no longer close. I have already tried turning the cap, but that does not solve the problem permanently. I suspect that the plastic cap becomes a little softer due to the warm tea (100°C is not that far from the glass transition temperature of PE/PP) and the holding force is therefore not sufficient. I have looked at other thermos flasks that I own and they all have a metal cap. So I suspect a general design flaw in the flask. Moreover, the thermos flask never seals perfectly.

Martin (24/03/2023), Austria
Orders: 5
Reviews: 6