Reston Lloyd is a leading manufacturer and distributor of kitchenware, specializing in enamel on steel products. For nearly 30 years, we have been dedicated to providing the highest quality products, with an equal emphasis on superior customer service. This Calypso Basics Micorwave Cookware /Storage Set is made of polypropylene. These 6pcs microwave set comes in 40-ounce, 28-ounce and 16-ounce with adjustable steamer lids that will allow the foods to retain their nutritional value as well as the fresh flavor in no time at all. It goes from freezer to microwave with no problem.