Professional Factory - Our 5L CO2 bottles are constructed from premium 1.5mm SUS304 stainless steel - 25% thicker than standard tanks. Far superior to plastic bottle generators, they're more durable, stable, safe, and high-pressure resistant. Premium Safety Protection -- Automatic pressure relief valve activates when CO2 pressure exceeds 30~35KG. 12V waterproof solenoid valve prevents leakage risks for complete safety. Professional DIY kit -- A complete system in 2L size bottle, that includes SUS304 stainless bottle, regulator, Solenoid valve, Filter, precision needle valve, and easily adjustable bubble counter High Precision -- having the 12V solenoid on a timer, you can specify when you want CO2 injection on and for how long. Bubble counter with check valve built-in. It stops water from back flowing into your CO2 tank Tips for All Users -- The required powders to generate CO2 gas are not included; you will need purchase the citric acid and sodium bicarbonate powders separately.