Nature’s Best® Roaster utilizes advanced engineering techniques, resulting in a 40% reduction in oil-based resins, while providing a structurally stronger container. Made of a unique blend of #5 polypropylene and natural resources. Contemporary design polypropylene lid is easily secured and will not crack like those made of polystyrene. Leak-resistant lid fit eliminates the need to over wrap with film or tape. Double vents allow steam to escape freely and anti-fog material formula reduces condensation buildup.