Each high quality glass jar features an airtight seal with replaceable rubber gasket to keep foods fresh longer, while the easy-open metal clasp safely keeps a lid on things! Chef's tip: extend the life of your reusable Fido jars by removing the rubber seal before placing the jars in the dishwasher. It's also a good idea to replace the rubber seal before reusing the lid. You'll want to store foods with a high fat content in a different container, as fat tends to adversely affect the rubber seal.