10 Mason Jar Fermenter Gaskets Wine Beer Fermentation Airlock Lids O Ring Silicone Grommets for Sauerkraut Homebrewing Fermentor Set Include : 10pcs/30pcs/50pcs/100pcs Condition : New Material : Silicone Color : Black(as pictures show) Features : Silicone Grommets for Mason Jar Fermentation Airlock Lids. Made of thicker silicone, BPA free, durable and long lasting. The washer will help maintain the ferment for a longer period. An airlock can be inserted in the grommet, fits airlock perfectly. Work with the airlock, makes a perfect air-tight seal to keep bugs/bacteria/oxygen from getting in your fermenter. Size : External diameter: approx. 15mm/0.6". Internal diameter: approx. 8mm/0.3", Height: approx. 8mm/0.3" Friendly Tips: The size is measured by hands, please allow minor error of measurement. Photo color might be a little different from the actual product due to color display of different monitors.