6/8/10/12mm Aluminum One-way Non-return Check Valve Fuel Water/Gas/Air Vacuum The smallest size of these One Way Valves is 6 MM, and the largest size is 12 MM. They can prevent fuel from returning back to the tank and holds it in the line so that the tube can be easily installed without falling off. Features: The life of Aluminum head for using is longer than plastic heads Arrow marked on valve, showing fluid flow direction, Prevents fuel from returning back to the tank and keeps it in the line. In this way, this product can perfectly solve the problem that your vehicle is hard or slow to start because the fuel is running back through the lines. Also great for water pressure pumps & galley pumps which are not self-priming Professional grade non-return valve - Ideal for marine, automotive, caravans/RV, and agriculture. Stable characteristics, high reliability. Easy installation and replacement. Specification: Material: aluminum alloy Product size: 6MM 8MM 10MM 12MM Product weight: 6MM: 19g 8MM:21.1g 10MM:20.6g 12MM:23.5g Advantages: diesel, gasoline, aging resistance Opening pressure: 0.2 bar Working pressure range: 0.2-6 bar Working temperature range: - 30 ℃ to 130 ℃ Scope of application: car, ship, helicopter, ship, motorcycle and other fuel systems Use medium: diesel, gasoline, water, etc. (not suitable for methanol, because the methanol will produce formic acid, it will corrode the inside of the product, which will lead to product failure) Package included: 1 x Fuel Non Return Check Valve Note: Please allow minor errors due to manual measurement. Thanks for your understanding. Monitors are not calibrated same, item colour displayed in photos may be showing slightly different from the real object. Please take the real one as standard.