With one-way exhaust valves, automatic venting to prevent air from entering the bottle to ensure that the food will not become affected by oxygen and dust. You don't need to open the fermentation lid every day, just release the positive pressure and maintain the water level. It is suitable for any wide-mouth mason jar with a diameter of 3.4 inches, or other jars with a diameter of 3.4 inches. Perfect for DIY making kimchi, fruit wine, sauerkraut, kimchi, ginger carrots, pickles etc. Easy to clean, the plastic cover can be cleaned in the dishwasher. Specification: Material: Plastic Diameter: approx.86mm/3.4in Optional Colors: Red, Blue, Hot Pink, Green, White, Lake Green, Gray Quantity: 1 Set Note: Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you Package Contents: 1 x Fermentation Lid 1 x Exhaust Valves (other accessories demo in the picture is not included.)