Tough Bands are designed to replace flimsy generic screw bands that are prone to warping and rusting. They fit on top of any standard Mason jar disc lid and are durable and reusable. Tough Bands are especially great for storing liquids and ferments because of their rust-proof nature. BPA and phthalate-free plastic lids and silicone gaskets. Dishwasher, fridge and freezer safe. Available in packs of 4 for wide and regular mouth Mason jars.