Abstract: The invention relates to a dosing device for fluids used in infusion or transfusion systems comprising a flexible fluid line transversing a housing to compress the fluid line. The device comprises a housing and an elastomeric tubular element having leading and trailing sections which traverses said housing to interconnect respective ends of said fluid line. The tubular element comprises a thicker portion between the leading and trailing sections whereby the thicker portion protects against longitudinal displacement of the housing. A pressing element engages the tubular element outside the region of the thicker portion.