These muffin cups are made of thick food-grade aluminum foil, which can hold the cups well. Just place them in the oven and bake them directly, no baking trays are needed. Made of high-quality strong aluminum foil, the surface is smooth, slightly waterproof and oil-proof, and can withstand temperatures up to 220 degrees Fahrenheit. Easy to carry-The sturdy cup with lid makes it easy for you to carry cupcakes without the need for a paper cup box. Multi-purpose-very suitable for indoor and outdoor use, picnics, camping, outdoor banquets, various parties and gatherings, etc. Save time-scrub the residue on the baking tray with your hands to save a lot of cleaning time and enjoy baking time.