Heard these were the way to go to avoid blisters and not overheat. Not impressed. I felt no difference with the heat factor, and they seemed rather rough on my feet. Decided instead to run in a Brooks moisture-wicking sock that feels really soft. I've heard using cornstarch on your feet absorbs the sweat to prevent blisters. Since using it I haven't had any running blisters, which includes running a marathon and 4 half marathons.