Hot and cold relief provided with the special Hydro-gel fill wrap to suit all your sinus and head needs. Semi solid water/glycerin based gel conforms to your body form and retains the shape. Even if punctured, gel does not leak. For hot wrap, heat in the microwave for two minutes and get relief for the next 30 minutes. As a cold wrap, freeze and then put on for 30 minutes to reduce swelling and pain. Covers are created out of unbleached cotton twill and can be hand washed. Last a lifetime. You deserve the care and comfort. Comes in one free size, to fit all.