When we say it doesn't sweat, we mean that it's not the same as coming into contact with a non-cotton surface during the summer months, like the surface of the stroller. So, that's the difference. If it avoids extra sweat, it avoids it. Otherwise, yes, if it gets warm, it will sweat. It fits perfectly on the Inglesina Trilogy stroller, the stroller doesn't get dirty, the fabric is such that it cleans very easily (basically like a white towel) and the child doesn't seem bothered.
I also have the corresponding cover for the car seat of this stroller system, also very satisfied, as in the car the heat is greater when you get in and it "collects" less sun, due to the color and fabric composition.
It's not a mattress at the same time, just a cover.
Durable in use.