CO2 Bubble Counter: With the use of the water meter, CO2 gas output can be clearly seen to provide sufficient CO2 demand for water grass. Safe to use: The nut locking system is designed to effectively lock the CO2 air hose to prevent accidents caused by loosening. Anti-reverse function: The patented anti-reverse design prevents liquid backflow when pressure changes, ensuring the water meter and CO2 cylinder are not damaged. Easy to install and use: remove the sealing ring and install on the trachea interface of the valve, then tighten the bubble counter. Add 4/5 of water into the bubble counter and tighten the top cover. Connect the CO2 hose and then tighten the trachea attachment nut. It is simple and easy to maintain using the replaceable parts design method. Size: about 21mm*79mm Color: silver Quantity : 1 piece Note: The data is all manually measured, please allow 1-3cm error, due to the difference in light and display, there will be some difference of color, the actual object received shall prevail.