A device for selectively regulating the flow rate of a fluid, comprising: a housing including an inlet and an outlet; a plurality of flow conduits fluidly connected between the inlet and the outlet each of the flow conduits including a resiliently compressible occlusion tube (316,318,320), the flow conduits being of substantially equal inside diameters, each of the flow conduits having a length representative of a different pre-defined flow rate; and a flow rate selection mechanism, operatively mounted in the housing, for selectively obstructing fluid flow through the flow conduits, thereby to provide a flow rate from the inlet to the outlet corresponding to the combined flow rates of the unobstructed flow conduits, wherein the flow rate selection mechanism comprises: a flow-blocking element operatively associated with each of the flow conduits, each flow-blocking element comprising a resilient element that is movable into and out of a flow-blocking compression against its associated occlusion tube, and being selectively operable to block fluid flow through its associated conduit; and characterised in that the device comprises: an actuation mechanism comprising a plurality of cam elements (242a,242b,242c), each of which is positioned operatively to move one of the resilient elements into a flow-blocking compression against its associated occlusion tube, and operatively engageable with each of the flow-blocking elements and movable among a plurality of pre-defined positions in all but one of which it operatively engages one or more of the flow-blocking elements to block flow through the flow conduit associated with each of the operatively-engaged flow-blocking elements, and in one position of which it operatively engages none of the flow-blocking elements, wherein each of the resilient elements comprises a resilient cam follower finger (212a,212b,212c) located so as to be operatively urged into a compressive engagement with one of the occlusion tubes when the cam follower finger (212a,212b,212c) is engaged by a cam element (242a,242b,242c); and a cam rotor rotatably mounted in the housing and having the cam elements (242a,242b,242c) disposed thereon in positions in which each of the cam elements (242a,242b,242c) may operatively engage an associated cam follower finger (212a,212b,212c) as the cam rotor is rotated, wherein the cam rotor is rotatable among a plurality of rotary positions, each of which is associated with a predefined fluid flow rate, so that rotation of the cam rotor incrementally increases the flow rate from zero to a maximum. a housing including an inlet and an outlet; a plurality of flow conduits fluidly connected between the inlet and the outlet each of the flow conduits including a resiliently compressible occlusion tube (316,318,320), the flow conduits being of substantially equal inside diameters, each of the flow conduits having a length representative of a different pre-defined flow rate; and a flow rate selection mechanism, operatively mounted in the housing, for selectively obstructing fluid flow through the flow conduits, thereby to provide a flow rate from the inlet to the outlet corresponding to the combined flow rates of the unobstructed flow conduits, wherein the flow rate selection mechanism comprises: a flow-blocking element operatively associated with each of the flow conduits, each flow-blocking element comprising a resilient element that is movable into and out of a flow-blocking compression against its associated occlusion tube, and being selectively operable to block fluid flow through its associated conduit; and characterised in that the device comprises: a flow-blocking element operatively associated with each of the flow conduits, each flow-blocking element comprising a resilient element that is movable into and out of a flow-blocking compression against its associated occlusion tube, and being selectively operable to block fluid flow through its associated conduit; and characterised in that the device comprises: an actuation mechanism comprising a plurality of cam elements (242a,242b,242c), each of which is positioned operatively to move one of the resilient elements into a flow-blocking compression against its associated occlusion tube, and operatively engageable with each of the flow-blocking elements and movable among a plurality of pre-defined positions in all but one of which it operatively engages one or more of the flow-blocking elements to block flow through the flow conduit associated with each of the operatively-engaged flow-blocking elements, and in one position of which it operatively engages none of the flow-blocking elements, wherein each of the resilient elements comprises a resilient cam follower finger (212a,212b,212c) located so as to be operatively urged into a compressive engagement with one of the occlusion tubes when the cam follower finger (212a,212b,212c) is engaged by a cam element (242a,242b,242c); and a cam rotor rotatably mounted in the housing and having the cam elements (242a,242b,242c) disposed thereon in positions in which each of the cam elements (242a,242b,242c) may operatively engage an associated cam follower finger (212a,212b,212c) as the cam rotor is rotated, wherein the cam rotor is rotatable among a plurality of rotary positions, each of which is associated with a predefined fluid flow rate, so that rotation of the cam rotor incrementally increases the flow rate from zero to a maximum.