Fermentation lids set includes: 4 stainless steel wide mouth fermentation lids, 5 silicone rings (4pcs inside,1pcs extra), 4 airlocks, 10 silicone grommets. Material: made of stainless steel, so they won't rust. all parts are removable, BPA FREE and food-grade material, dishwasher safe. (Note--Do Not sterilizing the plastic airlocks with boiling water) Reusable fermentation lids, the lid have a silicone ring/seal underneath to make things airtight. Silicone gaskets create a tight seal between the lid and the jar, preventing water, oxygen and dust from contaminating your ferments Fermentation lids fit 3.38inch (8.6cm) outer diameter mouth wide jars, Compatible for wide mouth mason jar in Ball, Pint, Quart, or Half-gallon. Fermentation kit: Begin making tasty, healthy kimchi, ginger carrots, Hot Sauce, sauerkraut, pickles, huckleberry mead, beer, wine, and other fermented foods with ease and safety.