Specification:12 sets of lids and bands;the inner diameter of the metal ring is 2.91 inch, outer diameter is 3.39 inch；the diameter of lid is 3.35inch.It cannot be used with a regular mouth jar. Material:They are made of stainless steel, not easy to rust,and can be used many times. Cleaned:you can wash in the dishwasher. After cleaning, please dry the glass bottle cap. Effect：It's easy to use as a storage，regular mouth mason jar lids create an airtight seal to keep food preserved. Upgrade: Regarding everyone's concern about the white coating of the wide-mouth lid rings, we have upgraded without any coating, and the lid is harder and safer. Can be used with confidence!