... surface,catch only by one hand,good quality and treatment,use for many years.It is normal to use even temperature less than -40 ... you add oil one time.Safety,no toxic, environmental protection.How to use:1.open the cover of warmer. 2.put it up ... ,etc.when weather being cold.Medical treatment: cure women dysmenorrheal,hand&feet cold, arthrosis,etc.Product characteristic:good quality,green environmental ...