Ball Regular Mouth Leakproof Lids feature a 1-piece, screw-on design that is leak-proof, airtight, freezer-safe and dishwasher-safe. Store your favorite recipes in iconic Ball jars and secure with Ball Leakproof Lids. The airtight seal is perfect for herbs, spices, on-the-go salads, smoothies, and more and is freezer-safe for storing jam recipes, sauces, and soups. Tip: When filling freezer safe jars, leave 1/2 inch headspace to allow for food expansion during freezing.