Small ACP-Roots pumps create, for example, the required fore-vacuum for turbopumps in particle accelerators. Large ACP 120 with their high pumping speed and low final pressure are used in freeze-drying applications. The A 100, A3P or A4 series dry pumps are used in large numbers as process pumps in the semiconductor and coating industry. Nevertheless, all of these areas have one thing in common: they require a clean and dry vacuum. The technology of the multi-stage Roots pumps is the perfect solution here. Lubricants and sealing material between the rotor and stator are not required by the frictionless working pumping module. Thus, hydrocarbon vapor backstreaming can be avoided. In the suction chamber of the pumps, no sealing materials are processed. This means the pumps are free of particles, extremely reliable and stable for a long period of time which results in low cost of ownership.