A lovely idea but the execution leaves something to be desired. Firstly, I am very particular about plastic and other chemicals getting into my tea and foods and what drew me to to this item at first was the glass interior. There is plastic in the construction of the lid and middle layer but at the time of my purchase these elements were made of polypropylene, which I deemed acceptable as it is one of the safer plastics. When cracks started forming in my first Libretea however, the company sent me a replacement with a changed design. During the intervening time, they had switched from using polypropylene to tritan, a plastic that is advertised as “BPA free” but which studies have shown to contain other chemicals with estrogenic effects similar to BPA. Don’t trust the “BPA free” buzzword, there are plenty of other chemicals in plastic that can cause harm, in many cases you are simply trading BPA for a different poison.
Secondly, as I mentioned before the first item I recieved developed some problems after use, with small cracks/lines appearing on the plastic side near the border between the plastic and glass. I have not used the replacement I was given since learning the plastic has been replaced by tritan so I do not know if this problem still persists.
Lastly, while the turn upside-down to steep idea is a good one, the steeping chamber itself is on the small side compared to the size of the thermos itself, making it difficult for some teas to expand. If you are dead-set on the idea of turning your travel mug upside down to steep, I would instead suggest one of the double-tiered glass travel mugs from china that one can find on ali-express. The steeping chambers for said items are made from plastic, but that too is the case with this product as well.