Heating cores help to cook the middle of cakes by conducting heat into the batter. Cakes bake and and rise evenly. To use: grease heating cores, and place in pan flat side down. Add batter, bake, and remove after baking. Made of stainless steel. Use all four cores for 16" or larger cake, 3 cores for 12 or 14", and 1 core for 10" or smaller cakes.