The outside bottom surface of the cookware must be made of a ferrous magnetic material such as cast iron, enameled steel, or magnetic stainless steel. The cookware's interior can be aluminum or other non-ferrous material with or without a non-stick coating as long as the bottom is ferrous.  If not indicated at the base of your cookware, it is easy to check whether or not your cookware will work by using a fridge magnet or any other permanent magnet. If the magnet sticks to the bottom of the pot/pan, the cookware will work on an induction cooktop.