A disposable flow set comprising: (a) a drip chamber or a spike; (b) a first administration tube-segment for administering liquid from said drip chamber or spike having a first end connected to said drip chamber or spike; (c) a pumping tube-segment having a first end connected to a second end of said first administration tube-segment; said pumping tube-segment of said flow set being suitable for installation in a liquid pump; (d) a second administration tube-segment having a first end connected to a second end of said pumping tube-segment; (e) an anti-free-flow valve at a second end of said second administration tube-segment; and (f) an identifying-key connected to said pumping tube-segment, said identifying-key being clamped on said pumping tube-segment and including: (i) a number of teeth with a unique combination of location and width, said teeth being insertable into compatible niches in a specific liquid pump so as to prevent insertion of said flow set to a non-compatible liquid pump; and (ii) a pressing-plate to be pressed by a door of the liquid pump in order to allow said pumping tube-segment to be pressed against a pressure-sensor of said liquid pump when the door of said liquid pump is closed to enable said liquid pump to use the sensed pressure to verify the presence of said flow set; said disposable flow set being characterized by: (g) a stretching-key connected to said pumping tube-segment; said stretching-key being clamped on the pumping tube-segment at a distance from the identifying-key and having a unique pattern to be inserted into a compatible recess in a specific liquid pump to prevent insertion of the flow set in a non-compatible liquid pump, and maintain the pumping tube-segment under tension, straight, and stretched to a determined degree when inserted into the liquid pump. (a) a drip chamber or a spike; (b) a first administration tube-segment for administering liquid from said drip chamber or spike having a first end connected to said drip chamber or spike; (c) a pumping tube-segment having a first end connected to a second end of said first administration tube-segment; said pumping tube-segment of said flow set being suitable for installation in a liquid pump; (d) a second administration tube-segment having a first end connected to a second end of said pumping tube-segment; (e) an anti-free-flow valve at a second end of said second administration tube-segment; and (f) an identifying-key connected to said pumping tube-segment, said identifying-key being clamped on said pumping tube-segment and including: (i) a number of teeth with a unique combination of location and width, said teeth being insertable into compatible niches in a specific liquid pump so as to prevent insertion of said flow set to a non-compatible liquid pump; and (ii) a pressing-plate to be pressed by a door of the liquid pump in order to allow said pumping tube-segment to be pressed against a pressure-sensor of said liquid pump when the door of said liquid pump is closed to enable said liquid pump to use the sensed pressure to verify the presence of said flow set; (i) a number of teeth with a unique combination of location and width, said teeth being insertable into compatible niches in a specific liquid pump so as to prevent insertion of said flow set to a non-compatible liquid pump; and (ii) a pressing-plate to be pressed by a door of the liquid pump in order to allow said pumping tube-segment to be pressed against a pressure-sensor of said liquid pump when the door of said liquid pump is closed to enable said liquid pump to use the sensed pressure to verify the presence of said flow set; (g) a stretching-key connected to said pumping tube-segment; said stretching-key being clamped on the pumping tube-segment at a distance from the identifying-key and having a unique pattern to be inserted into a compatible recess in a specific liquid pump to prevent insertion of the flow set in a non-compatible liquid pump, and maintain the pumping tube-segment under tension, straight, and stretched to a determined degree when inserted into the liquid pump.