Product name: CT Series Aquarium Aerator Ultra Silent Aquarium Air Pump Air Compressor Oxygen Airpump Single & Double Outlet Product description: 1. Adjust the air volume left and right through the knob;2. Stainless steel vent holes, corrosion-resistant, not easy to rust, and even venting;3. Anti-vibration, reject noise.CT-101 single holePower 3WAir output: 1.5L/minsize: 11x6,5x4.5cmSuitable for fish tanks within 0.3 metersCT-201 single holePower: 4WAir output: 1.5L/minsize: 12x7x6cmSuitable for fish tanks within 0.3~0.5 metersCT-202 double holePower: 4WAir output: 1.5L/minsize: 12x7x6cmSuitable for fish tanks within 0.5~1.2 metersCT-402 double holePower: 4WAir output: 2.8L/min*2size: 15x8x6cmSuitable for fish tanks within 1.2~1.5 metersCT-404 four holesPower: 8WAir output: 2.8L/min*4size: 15x15.5x6cmSuitable for fish tanks within 1.5~2.0 meters