A parallel assembly (2; 11; 51) of chromatography column modules (3a,b,c; 13a,b,c; 53a,b,c, 90a, b), the assembly having one common assembly inlet (15; 55) and one common assembly outlet (17; 57), each column module comprising a bed space (29) filled with chromatography medium and each column module comprises integrated fluid conduits which when the column module is connected with other column modules are adapted to connect the bed space (29) of the column module with the assembly inlet (15; 55) and the assembly outlet (17; 57), wherein the total length and/or volume of the fluid conduit from the assembly inlet to one bed space together with the length and/or volume of the fluid conduit from the same bed space to the assembly outlet is substantially the same for all bed spaces and modules installed in the parallel assembly.