Product review (1 stars): Baker Beware!
Do NOT put on bottom burner if you plan on cooking on 400 degrees or higher. Had these on both racks & the bottom one basically disintegrated after baking some potatoes for a hour  at 425. Top rack one who's was further away from the heat source at the bottom of the oven survived. Figured I can't send them back since 1 is used & the other one is in pieces.