This is a new stainless steel check valve designed for use in aquarium CO2 injection systems. Its primary function is to prevent water backflow, protecting your regulator and other equipment. The stainless steel construction offers good corrosion resistance for long-term use in a wet aquarium environment. This valve is a practical component for maintaining a safe and efficient CO2 setup, suitable for freshwater or planted tank hobbyists. Free shipping is included with your purchase. As specific dimensions and connection sizes are not listed, please check the product listing for full details to ensure compatibility with your existing tubing and equipment. Stainless Steel Check for Valve for Aquarium CO2 System Anti-Backflow Rust. Condition: New, Made in China. Listed at 8.92 USD. Features: This check for valve is only suitable for CO2 equipment. Made of high quality stainless steel, it is not rusted and durable. Easy to install and use, simple and convenient. Prevent water from entering carbon dioxide. Do not use with air pumps and air compressors. Specifications: Material: Stainless steel Color: Silver Size: Length: app.4.7 for cm/1.85 in;Caliber: app.4 mm/0.16 in Package Includes: 1 x Aquarium check for valve note: 1. Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. 2. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you!