Abstract: A twin filter for compressed air, in which there are two filters set in parallel and an arrangement of valves to direct compressed air through a selected filter. The arrangement of valves includes inlet valves to distribute compressed air from the inlet to the selected filter and an arrangement of counter-valves to direct the compressed air from the selected filter to the compressed air outlet. The arrangement of counter-valves includes a ball chamber formed in the housing structure, at the ends of which are inlet connections and an outlet connection in the center. A ball is arranged to close that inlet connection in which there is no pressure. The ball chamber has a filter element in the central area of which a ring-like outlet channel is formed, which collects the outlet flow to the outlet connection.