Non-toxic, reusable and portable. Provides relief from migraines and sinus pain. Also soothes & minimises the appearance of under eye circles and uses heat to treat aches, pains, congestions & headaches. Features an adjustable velcro strap for all sizes of heads. Simply flex the button repeatedly until it clicks to begin the crystallisation process. To reactivate, place in water & bring to the boil for a few minutes until the crystals liquify. Allow to cool & store at room temperature until next use.