A compressed air supply device for a commercial vehicle is provided. The compressed air supply device includes a valve housing and an essentially axially symmetrical, exchangeable air-drying cartridge which is connected to the valve housing. The valve housing and the air-drying cartridge are connected via an essentially circular seal which lies in a plane perpendicular to the axis of the air-drying cartridge. The valve housing and the air-drying cartridge can be coupled to each other by being brought together in an axially parallel manner. The valve housing and the air-drying cartridge have features which permit a leak-proof connection between the valve housing and the air-drying cartridge at one or more angular positions of the air-drying cartridge relative to the valve housing.