[This review was collected as part of a promotion.] The double walls makes them a little bit bigger than a typical espresso mug, and therefore easier to hold. They also keep it from burning my hand.
[This review was collected as part of a promotion.] I looked high and low for high quality double wall glass mugs in various sizes. I purchased the 2.7oz and the 4.5oz. I can use it in microwave and the shape is elegant. So happy with my purchase