THIS IS ALUMINUM MUFFIN PAN, FOR THE BEST BAKING RESULTS, THE PAN SHOULD BE ABOUT 2 INCHES SMALLER THAN THE INSIDE OF THE OVEN, TO ALLOW FOR PROPER AND UNIFORM HEAT CIRCULATION. THIS PAN MEANS YOU CAN PUT FEWER PANS IN THE OVEN AT ONCE, BUT BAKE MORE MUFFINS OR CUPCAKES AT ONE TIME... AND SPEND LESS TIME IN THE KITCHEN AND MORE TIME EATING DELICIOUS TREATS!