Contrary to the description it does not hold heat 12h, hot coffee is cold after 4h. Standard thin steel walls, as in all products of this type. The stopper must be tightened firmly, otherwise it leaks when shaken. Quite a lot of liquid remains on the walls of the mouthpiece (in the grooves of the cork) after drinking, so there is no "click, drink, click, throw it in the backpack as it goes". - has to stand upright. Somehow, the liquid flows poorly, I even unscrewed it to see if it was the end of the liquid, but no.... On the plus side, the plastic of the mouthpiece is pleasant to the touch and thin.