It emits carbon dioxide during honey, white wine, milk wine, and alcohol fermentation while preventing oxidation. Easy to use: fill water into the exhaust valve, insert it into the brew barrel cover or rubber plug on the top of the fermentation container, and secure with the lid. Effectively prevents insects from entering the wine or beer with the included cover. The entire fermentation process is automatic, requires no manual control, and the product can be reused for an extended period. Suitable for pure juice fermentation, such as white grapes, honey wine, and secondary fermentation of red wine. Specification: High Quality Material: High-quality plastic (eco-friendly) Color: Transparent as shown in picture Sub-Type: Airlocks Size: Length 17cm / 6.6 inches Package includes: 5 pcs exhaust valves Note: Conversion: 1cm = 10mm = 0.39 inch Please allow 1-3mm error due to manual measurement. Ensure you are comfortable with this before purchasing. Due to differences in monitor displays, the picture may not reflect the actual item color. Thank you.