I ordered a large Chillys bottle for my recent holiday to Africa as I knew my hotel room didn't have a fridge. I was a bit worried that this bottle wouldn't work as claimed in such a hot sunny climate but I was gladly proved wrong and was quite the best purchase I have made. The daytime temperature was 36 degrees falling to 29 or 30 degrees at night time. Cold Water poured into the bottle at about 5 pm remained cold all night and was still cold when I hit the again at 10 am the following morning! The sun on the beach also made the outside of the bottle hot, but again water remained cold inside! I wholeheartedly recommended to other guests. Am delighted with my purchase!! Thank you. Unfortunately the outside colour does get marks but that is just a cosmetic problem.