This perforated baking sheet allows greater and more even contact with the heat of the oven. The 1/4" (6mm) perforations allow for the food to be exposed to the heat of the oven. This is perfect for baking breads and for use in conjunction with a silicone baking mat. The perforations account for 60% of the total surface of the sheet. It is made of aluminum and has shallow, flared edges. Two sizes available.