Features: brand new and high quality To stop water come into CO2 Equipment - Dioxide Cylinder. Our one way check for valve can prevent the aquarium from water flowing back, which is caused by the decrease, and keep the function and service life of Carbon dioxide bottle. The one way check for valve is suitable for CO2 supply system in fish for tank, aquarium and others. Made from premium stainless steel materials break and rust resistant and cleans easy.Small and compact, about 4cm long. Attention: FOR CO2 SYSTEMS ONLY Please do not use this CO2 Check for Valve to work with Air pump Air Compressor. This CO2 Check for Valve only to work for CO2 Equipment. Package Includes: 1x Aquarium Water Check for Valve for CO2 Equipment Specifications: Material: Stainless Steel Size: Approx.4x0.8cm/1.57x0.31in Air Inlet/Outlet Tube Calibre: Diameter4mm note: 1.Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item.