1. the jar lids are made of tinplate and the lid covers a ring which made of pvc; they are rustproof and durable, can be applied for many times use; high and low temperature resistant, so can be served in refrigerators, dishwasher and microwave ovens. 2. The sealing ring inside the jar lid makes the mason jar canning jar lids have good sealing performance, air tight and escape free, the seal tightly ensure that it is suitable for keeping food, grains, dressings, drinks fresh, no need to worry about leakage that may contaminate the kitchen or other places after sealing materials. 3. suitable for sealing mason canning jars that stored spices, candy, cookies, fruit, jam, soda, tea or coffee, nails, screws and other small objects, make sure the size before purchase . 4. The edge of the mason jar lid is designed with the line so that increasing the friction force to open the jar.