The 17 mm Seachem Glass Bubble Counter Diffuser is a highly effective way to disperse CO2 throughout your planted aquatic system. The pollen-style diffuser is compatible with 6 mm (1/4") standard airline tubing and connects directly to CO2 injection systems. The sleek, low profile unit helps to minimize visual distractions within the tank and boasts a 17 mm large surface area disc that provides diffusion for large volumes of CO2 gases. The inclusion of a bubble counter in the diffuser makes the use of a bubble counter on the CO2 tank or in-line unnecessary. Suction cups included with the unit. Well suited for aquariums between 20-60 gallons.