A fluid processing system comprising a fluid processing unit and a tubing arrangement providing fluid flow to and from said fluid processing unit ; wherein said tubing arrangement comprises one or more flow cells , each one of said flow cells comprising a body having an inlet and an outlet and a fluid flow channel extending from the inlet to the outlet of the body , said body further comprising a receptacle comprising a chamber forming a part of the fluid flow channel of the body , said chamber comprising a first opening for connecting a functional element to the flow cell such that the functional element is in contact with or exposed to a fluid flow passing through the fluid flow channel; a functional element ; a first tubular connector arranged adjacent to the inlet of the body ; a second tubular connector arranged adjacent to the outlet of the body ; and a fluid flow path extending from the first tubular connector through the inlet of the body , the body and its receptacle to the outlet of the body to the second tubular connector ; wherein said fluid processing unit is selected from a unit comprising a single use tangential flow filtration mobile skid and a unit comprising a device for chromatographic separation, wherein said fluid flow path of the flow cell has a predetermined, consistent cross-sectional area at least within and along the first and second tubular connectors , and wherein the volume of the chamber of the body of the flow cell is designed to provide a cross-sectional area of the fluid flow path equal to or larger than the cross-sectional area of the fluid flow path within and along the first and second tubular connectors , also once the functional element is mounted in the opening and optionally extends into the chamber . a body having an inlet and an outlet and a fluid flow channel extending from the inlet to the outlet of the body , said body further comprising a receptacle comprising a chamber forming a part of the fluid flow channel of the body , said chamber comprising a first opening for connecting a functional element to the flow cell such that the functional element is in contact with or exposed to a fluid flow passing through the fluid flow channel; a functional element ; a first tubular connector arranged adjacent to the inlet of the body ; a second tubular connector arranged adjacent to the outlet of the body ; and a fluid flow path extending from the first tubular connector through the inlet of the body , the body and its receptacle to the outlet of the body to the second tubular connector ; wherein said fluid processing unit is selected from a unit comprising a single use tangential flow filtration mobile skid and a unit comprising a device for chromatographic separation, wherein said fluid flow path of the flow cell has a predetermined, consistent cross-sectional area at least within and along the first and second tubular connectors , and wherein the volume of the chamber of the body of the flow cell is designed to provide a cross-sectional area of the fluid flow path equal to or larger than the cross-sectional area of the fluid flow path within and along the first and second tubular connectors , also once the functional element is mounted in the opening and optionally extends into the chamber . <EOS>