These are actually Weck reusable Glass Lids. Made of the highest quality glass, they contain NO BPA! (Bisphenol A), lead, mercury or cadmium.
Available in Sizes - Medium - 90mm / 3 1/8" Large - 110mm / 3 7/8 ".
Perfect for using with Weck or Ball Mason jars. Keeps the fermenting fruit or vegetables from coming above the liquid.