Piston pumps are used for most large scale vacuum applications. These pumps have got a sliding sleeve Rotary Piston Vacuum Pump through which the gas enters, then drawn right into a cylindrical chamber and exhausted by a rocking piston plunger. These pumps are very hardy and also have pumping speeds that range from 15 cfm to 2,000 cfm and the pumps can reach a pressure of 1 1 x 10-4 Torr. Rotary piston pumps could be ready for corrosive and oxygen assistance.