These molds are crafted with a top quality plastic, that is made extra strong and able to withstand oven temperatures of 335 degrees in an oven. DO NOT OVER COOK OR USE a higher temperature! No need for silicone spray or Pam. They come out of the molds easily AFTER cooling! No metal warping. Measurements are at tallest and widest parts of the mold. It is not by a squared measurement. Sizes may slightly vary in measurement.