Each pad is small and fits in your palm.  First time you use the item, it takes a minute rub the fluid and click the metal inside and get the fluid around the metal all together to get it turning hot.  DON'T FREEZE, only put in fridge to get it cold for cold use,
If it is hard and used, boil water to return it to fluid, put a towel in the pan or pressure cooker so you don't melt the plastic on the pan. There are no returns if damaged.