Scientific design lets in just the right balance of moisture and dryness to keep your last slice of bread as tasty and fresh as the first slice! Made of clear, see-though polystyrene and holds a standard 1 lb. loaf of bread, and as the bread is used, sections push together (goes from 11" to 6") reducing the air space keeping the breads unbelievably fresh. Also keeps cakes and rolls moist and delicious.