For the safe, loss-free conduction of CO2 gas in CO2 fertilizer systems for aquariums To use: cut the hose to the correct length before insertion. Always keep hose length as short as possible Dedicated CO2-resistant hose, for all standard CO2 systems, colors: black or transparent/white Loss-free transport of CO2 gas. Normal air hoses are NOT CO2 gas resistant! Package contents: 1 dedicated CO2-resistant hose, length: 3 m, Ø 4/6 mm