While it is quite a quality product, as negatives I would first say that it does not have a lid to protect the mouthpiece from the straw, so in order to open and close it, you have to directly hold the mouthpiece, and secondly, no matter how tightly you close it, there is a small leak in the head and I consider that because of this, the initial temperature of the liquid is not maintained 100%.

Very good temperature preservation. Even ice cubes remain intact for hours before melting. The downside is that there is a small leakage from the top (straw). Also, poor construction both in the collapsible straw inside and in the corresponding collapsible brush (which broke on the first use).