Hand hold Air Pump Application For high school experiments Structure Air inlet Air outlet Outlet valve film Spring Piston cover Valve pole sealing circle Outer valve pole Outer cylinder valve sealing circle supporter How to use and maintain: Choose the air inlet or outlet for experiments. Use a hand or foot to make the valve move back and forth. Due to aging of the sealing circles, they should be changed at intervals. Spare parts One valve sealing circle Two valve pole sealing circles Two air outlet valve films