9v DC Mini Air Pump for Multiple Applications. Sphygmomanometer air pump, used in medicine multiple Applications. Best for DIY Kit Fish farming for oxygen supply; using a mobile phone charging head or a 6-volt power supply, the noise is large, but the gas volume is large, and it can be used for oxygen fishing in the wild; mute, it is recommended to use DC 3 volts, which reduces the gas volume and also reduces the noise. and Experiments. Completely maintenance-free, and no oil pump, do not pollute the transmission medium. Small, stable and reliable, hand-held instrument for pump-priming, low noise, low power consumption. Especially suitable for high environmental requirements.