Both dome lid and base (combo pack) are made with microwavable polypropylene. The contemporary design lid is easily secured to the base and will not crack like polystyrene. Leak-resistant lid eliminates messy spills and the need to over-wrap or tape. Unique venting allows steam to escape, and the integral anti-fog material formula reduces condensation for maximum food visibility. Raised ridges in the base drain juices away from the chicken to maintain freshness. The Roaster Grande holds a whole chicken up to 6 pounds (pre-cooked weight).