Platinum Silicone Sealing Rings Gaskets for Leak Proof Mason Jar Lids (10 Pack, Regular Mouth) 10 Reusable Seals for *Regular Mouth* Mason Jar Lids. Regular Mouth Mason Jars are 2 3/8" Internal Diameter. Leak Proof and Air Tight - For Ball plastic storage caps, MJL stainless steel storage lids, and many other lids. Fits and Seals Better Than Other Brands - Thicker and with a groove. The groove goes up, toward the top of the lid. Safest Material - BPA and Plastic Free. Made of platinum cured silicone rubber, these seals are dishwasher, freezer, and microwave safe! Silicone is a safe, green, material for food use that does not leach chemicals. Platinum cured silicone is more expensive and higher purity than FDA food grade silicone. Many Uses - Perfect for fridge and freezer storage, pantry storage, transporting food or beverage without leaking, home made fermenting lids, and much more! Not for canning.