This item is advertised as being able to withstand heat up to 450 degrees. I accidentally left it in the microwave and used convection at 350 degrees. The cover had completely melted and coated the bottom of my microwave with melted plastic. I'll probably spend 2 hours chiselling out the plastic.I'm upset that I lost money on this product, but moreso that it should not have happened had their marketting been true. I'm thinking about mailing the hunks of plastic to them to try and get a replacement.