A cartridge assembly for an adjustable fluid flow control device comprising: a rotor assembly comprising a base with a central aperture, a magnet mounted in the base and a protrusion extending from a lower surface of the base; a cartridge housing comprising a central rotor pivot configured to engage the central aperture, a stair-step array and a plurality of stops each projecting from an inner wall of the cartridge; wherein the rotor assembly is configured for placement at least partially within the cartridge housing and the protrusion is configured to be located between pairs of adjacent ones of said plurality of stops when resting on each step of the stair-step array, the protrusion configured to rest on a first step of the stair step array between two stops of the plurality of stops such that the rotor assembly is in a first, locked position in the cartridge housing with respect to the central rotor pivot; and characterized in that : the rotor assembly is configured to magnetically couple to an adjustment tool whereby the rotor assembly is configured to lift upwardly with respect to the stair-step array and the stops upon magnetically coupling with the adjustment tool; and wherein the rotor assembly is configured to rotate about the central rotor pivot when the rotor assembly is lifted such that the lower surface of the protrusion is positioned above an upper surface of the plurality of stops. a rotor assembly comprising a base with a central aperture, a magnet mounted in the base and a protrusion extending from a lower surface of the base; a cartridge housing comprising a central rotor pivot configured to engage the central aperture, a stair-step array and a plurality of stops each projecting from an inner wall of the cartridge; wherein the rotor assembly is configured for placement at least partially within the cartridge housing and the protrusion is configured to be located between pairs of adjacent ones of said plurality of stops when resting on each step of the stair-step array, the protrusion configured to rest on a first step of the stair step array between two stops of the plurality of stops such that the rotor assembly is in a first, locked position in the cartridge housing with respect to the central rotor pivot; and characterized in that : the rotor assembly is configured to magnetically couple to an adjustment tool whereby the rotor assembly is configured to lift upwardly with respect to the stair-step array and the stops upon magnetically coupling with the adjustment tool; and wherein the rotor assembly is configured to rotate about the central rotor pivot when the rotor assembly is lifted such that the lower surface of the protrusion is positioned above an upper surface of the plurality of stops. the rotor assembly is configured to magnetically couple to an adjustment tool whereby the rotor assembly is configured to lift upwardly with respect to the stair-step array and the stops upon magnetically coupling with the adjustment tool; and wherein the rotor assembly is configured to rotate about the central rotor pivot when the rotor assembly is lifted such that the lower surface of the protrusion is positioned above an upper surface of the plurality of stops. <EOS>