Superior Heat Conductivity: Pure aluminum construction allows for excellent heat distribution, delivering evenly baked goods each time you use the baking sheets. Warp Prevention and Durable Design: Naturals Bakeware is durable, and will never rust, providing you with long-lasting use. Encapsulated galvanized steel rims stand strong against warping, preserving the shape and quality of your pans through numerous uses. Two sheet pans come with convenient lid for transporting and storing your baked goods. Lid is made of BPA and Melamine-free polypropylene. Half Sheet Pans exterior dimensions 17.9 x 12.9 x 1 inches and cooking surface 17.1 x 12.1 inches.