This video shows a test of the basic idea behind the Eco-Cooler Zero Electricity Air Cooler ([ Ссылка ]). They make this specific claim:
"Hot air enters the bottles from the outside and then sends cooler air out of the thinner neck." Let's see if it's true!
![](https://s2.save4k.ru/pic/SuuNlZIbgrM/maxresdefault.jpg)