Our eight and fifteen gallon fermenter gasket is designed for those brewers or wine makers that wish to seal the tank. We believe the fermentation process works better if there is less pressure on the live yeast. The lid on the 8 and 15 fit tight enough so we believe a seal is not needed. The CO2 builds up and then leaks out around the edges of the lid. For bacteria to enter into the tank it must go up the edge of the lid over and down into the tank. We do not believe this will happen. We also sell a CO2 Injector Kit. Wine generally does not produce as much CO2 as beer. With our Kit CO2 can be added to force air out of the tank leaving a blanket of CO2 covering the wine. See the CO2 Injector Kit page for more details. Our gaskets are made from red FDA approved silicone. The ends are vulcanized together forming a circular ring. Please see the parts page for the airlock, fitting and clamps.