Abstract: A flow restrictor is made by flattening a tube of flexible material about a member of cross-sectional characteristics representative of a desired flow passage, and securing the tube there, e.g. by rf welding. The member is then removed leaving a determinate flow passage in which problems of creep do not arise. The restrictor may have parallel to the flow passage a portion of the tube which is not permanently secured together so as to leave a by-pass which can be open to give a comparatively unrestricted flow passage or can be temporarily completely closed by external compression. A single tube may have in line a plurality of such restrictors with by-passes, the flow passages of the various restrictors being of different flow characteristics. The flow characteristic required is obtained by closing off the by-pass associated with the selected flow passage.

Abstract: A seal in or for a blood bag has a first tamperproof seal consisting of a tube with an end wall separated by a line of weakening from an access passage. The line of weakening is torn open to gain access to the passage. The end wall is attached also by a flexible strap, and the action of tearing the line of weakening open renders available a plug also borne by the strap. Resealing by this plug is also tamper-proof in the sense that the plug cannot be removed without evidence that removal has been done or attempted.