Green Safes eco-friendly compostable cold cup lids are made from corn! This plant-based material is polylactic acid (PLA) also referred to as Ingeo. These lids are a great alternative to petroleum-based products. For convenience, most cold lids fit cup sizes 9oz-24oz. Intended for temperatures below 120 degrees, freezer safe, not microwavable, and will commercially compost within 90-120 days.