The purpose of overwrap bags is to shield the sample and main freezing bag from damage. To suit varying product storage quantities and types, FEP overwrap bags are produced in a range of sizes. The Overwrap bags are made to exactly fit inside the cassettes you already have. Heat sealing is compatible with bags. They are incredibly resilient to tearing and damage. They are the best option for the preservation and protection of biological samples since they are optically clear and allow for adequate sample visibility even at very low temperatures.