I have had few opportunities to use handwarmers so far. It is great to say they do put out a decent amount of heat and I really like the 3 settings for how hot they can heat. I do have two things that are tough, when on the high setting the batteries really do not last very long about 3 hours. Second the ends (where there is no cork) have been dented a few times, my guess is it is hitting my keys in pocket. I was hoping these would be way more rugged. I hope this does not shorten the life of the product, but only time will tell that.