I'm a physical therapist who first encountered these packs at a clinic where I worked. I soon discovered these cold packs worked far better than any other I've ever used. They are colder than gel packs and refreeze usually within 30 minutes. The covers provided are extremely convenient! No more searching for a pillow case to protect your skin. And towels are too thick to allow proper cooling of the area. I highly recommend this brand! I have several in my freezer at home for personal use.