These lids are made from renewable corn based PLA. This material is 100% compostable. Heat tolerant to 110 degrees Fahrenheit (Note: food should be allowed to cool prior to applying lids). Not recommended for hot liquid foods as the lids are vented and fit loosely. This item is not oven or microwave safe; lids must be removed prior to reheating. Side vent feature allows heat and steam to escape to protect against melting. Side vents allow stacking of multiple meals for transporting. Meets ASTM D-6400 standard for compostability. Meets FDA standards for food contact. Gluten-Free.