Tempered Glass Fermentation Weights for Lacto Fermenting in Wide Mouth Mason, Ball, Canning Jars (6 Pack) 6 Pack - Fits *Wide Mouth* (3" internal diameter) Mason Jars - Holds your ferment under the brine, leaving a tiny space around the edges to let out fermentation gasses. Glass does not leach anything into your food. Highest Quality Glass - Tempered soda-lime glass is the same type Mason jars are made from. Most competing products are not tempered. Dishwasher safe. Will Not Crack - Air bubbles in lower quality untempered glass can cause it to crack or break during fermentation. We found the sharp edges could chip, so we are sanding each weight by hand to round off the edges. Big, Thick, and Heavy - 68.5mm (2.7 inches) in diameter and 18.5mm (.73 inches) thick. 6 ounces each (170 grams). Use 1 or 2 Per Jar - If you fill your jars up to the neck, one weight will perfectly cover your ferment. For more active ferments, you will want to leave more head space and use 2 weights.