I had tried these tumblers while visiting family in Florida and was very impressed with the sweat free exterior even under the most hot and humid conditions.  So, when I saw them on Amazon I had to try a set for myself since I got tired of  wiping the moisture off of the outside of my glass while trying to enjoy a cool glass of iced tea. These tumblers can be either washed by hand  or put on the top rack of your dishwasher.  I recommend this product after using them on many occasions and even though the price is a bit steep they are as good as described!