The Klean Kanteen Swing Lock Cap Gasket is for the Swing Lock cap, perfect for beer, water, or any beverage, and sees heavy use. Because it's used frequently, it's a good idea to wash it regularly and alternate between them, replace it, or buy a new one if you lose it. This gasket is essential for maintaining cleanliness. ● Material: Silicone ● Compatible with: Swing Lock Cap