Safe material: The 6 piece fermentation airlocks are made of pp plastic, not cause any harm to the human body, nor any pungent smell, airlock grommets are made of silicone, and soft, safe for your using Airlocks for fermenting set with 6 pieces plastic airlocks and 24 pieces silicone grommets,it is strong and for your long time use Completely sealed:Just drill a 3/8 inch hold on your fermenter lid ,then use the black grommet insert into the lid hole,perfect for allowing fermentation gases to escape without allowing oxygen to enter,can make a good seal Widely use: the airlock kit for brewing craft beer, wine, sauerkraut, , hard cider, fruit wine, rice wine, carrots and ginger, ,tastes very good Easy to clean:The fermentation airlock easy to clean,this airlock can be separately taken out and cleaned,it can be easily cleaned with hot water or a simple detergent, very convenient and simple Colour: parent white Material: plastic Package Contents: 6 x Three-sheet check valve 24 x black sealing ring Only the above package content, other products are not included. Note: Light reflection 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.