Quality materials: our arilock grommet is made of silicone and PBA which is and to high temperatures for long-term use Good performance: this fermenter lid grommet is easy to install into the lid and hermetically sealed to protect food from oxygen; You can use this amazing product with airlocks to keep the fermentation for a longer period of time Hermetic sealing: this silicone grommet is well combined with the airlock and has a good hermetic seal to prevent oxygen from entering the fermenter; This helps to keep the enzyme fermented for a long time Quantity and size: you will get 50 arilock grommet with an outer diameter of 5/8 inches and an inner diameter of 3/8 inches; You need to drill a 5/8 inches hole in the fermenter lid; Then the airlock grommet is very easy to insert cover hole Wide use: this airlock gasket is suitable for any type of airlock and plastic lid and straw; Use these silicone gaskets to convert Mason jars into airlock fermentation vessels Features:Made of and long lasting silicone, the airlock grommet with good hermetical sealing performance fits most airlock and you can use the airlock grommet to turn mason jars into drinking bottles. Various application: This airlock grommet fits well with most types of airlocks and plastic buckets lids and straws. It is much convenient to make your own airlock lids for fermenting with our useful product. Easy installation into a bucket lid and provides a good sealing. Specification: Colour:black Material:rubber Size:Outer diameter: 1.59cm Package Contents: 50 * Exhaust valve gasket Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.