IT IS NOT A THERMOS. The product is excellent. The quality of construction, its design, and attention to detail (rubber on the bottom outside, to prevent slipping and easy breakage) are exceptional, but it is simply a metal bottle. I do not consider myself an expert, so I did not write a review from the first day, but as soon as I filled it with cold water from the fridge, I immediately felt the low temperature on the outside and moisture formed instantly. It surprised me because I know that a thermos should not react like that, but I thought maybe it is some new technology. Within 2 hours, the water had warmed up. To eliminate any doubt, the next day I compared it with another regular bottle with water at the same temperature, and both had the same performance in maintaining the water temperature. I also visited the website of the company that manufactures it, and this specific type/series of bottle is not mentioned as a thermos. So I am absolutely sure about what I am writing to you. I will keep it because it is indeed an excellent product as a bottle, but IT IS NOT A THERMOS. Please be more accurate with your listings