The 9 to 24 oz Green Ease flat Lid fits 9, 12, 16, 20 and 24 oz cups. It is a flat lid with a X-slot straw hole. These lids are made out of corn starch, meaning that they come from corn and can be returned back to the earth through commercial composting. Green Ease cold cup lids can withstand heat up to 110°F, which isn't very hot at all! If they come in contact with heat they will melt and deform.