Beautiful mugs and very lightweight, as if they are not made of glass - it seems that borosilicate glass differs greatly in weight from regular glass. The coffee, ice cream, or even milk looks truly delightful in these mugs. Everything was fine until now. However, I started to notice fogging, traces of moisture, and even water droplets while they had been washed and dried. And here’s what happened: water and moisture remained BETWEEN THE OUTER AND INNER WALL. You may have noticed fogging and moisture in aluminum constructions with double glazing if water gets into the middle. This happened here too, probably due to the slight depression at the bottom, which I don't know the purpose of - venting or air intake, or perhaps a manufacturing issue due to the double wall? The point is that the beauties are ruined, and I've lost all desire to use them. If a (very small) circular recess at the bottom is necessary for the construction of a mug, glass, etc., with double-walled glass, then it's not worth discussing