Manual Vacuum Pump Application: suitable for extracting experiments in elementary and high schools. Max. less than 1 (133Pa) Structure and features There are double cylinders, pistons, crutch crankshaft, connecting rod, sealing films and spring in a sealed container. One end of the crutch crankshaft protrudes out from the container and has a hand-rotating wheel. This wheel drives the crutch crankshaft to rotate and make two pistons move up and down. Thus, it extracts air to the outside. The air inlet of the container is in the middle and the air outlet is on the top. This device is effective and efficient due to the double cylinders. 3. How to use: before extracting, connect the device and the container to be extracted with a tough rubber pipe; a soft pipe won't work because it will become flat and thus block the air path. Rotate the hand wheel to extract.