Leakproof Cover: Our bamboo bottle caps are made of high-quality materials and are equipped with a removable silicone ring underneath, which can prevent your jars from warping and form an airtight seal, sturdy, durable and leak-proof, helping your jars stay fresh. Compatible Model: These tank storage lids are compatible with wide mouth mason jars. They can also use water cups and food storage tanks. How to Avoid Mold: 1. Clean the lid after use. 2. Do not use water higher than 85 degrees. 3. When not in use, do not store any liquid in a glass bottle. 4. Not suitable for preservation or immersion in water. Specification: Material: bamboo Color: as picture shown Packing List: 4*Bamboo Jar Lids