Harfield Hermetic Lid Polycarbonate. This Clear Hermetic Tumbler Lid is compatible with our 350ml Frosted Tumbler (Product Code: CF002CL) and 275ml White Cups. The cover gives an airtight hermetic seal to the food contents, which makes it perfect for food storage and will keep your ingredients fresher for longer. The lid also allows for the tumblers to be stackable, while in use so meals can be prepared in advance. Our lids are dishwasher and microwave safe for reheating food. The lid is made of polycarbonate, which is virtually unbreakable. The lid is very handy, when the compatible tumblers are used as dessert, snack or fruit pots.