Standard lids are tin-plated with a lacquer coating, double-coated on the inside to food grade and single-coated elsewhere.
When preserving, lids are placed on the bottle on top of the preserving ring and secured with a clip. When first put on the bottle, the lid appears convex, which will change to concave after processing, indicating the vacuum seal has formed.
Size 4 Preserving Lids fit bottle sizes 31, 36 and 65