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.