A fluid flow control device, comprising: a body comprising an inlet port, a control port, a common port, and a discharge port; a supply path extending between the inlet port and the common port; an exhaust path extending between the common port and the discharge port; a supply port disposed within the body along the supply path between the inlet port and the common port; an exhaust port disposed within the body along the exhaust path between the common port and the discharge port; a bypass port disposed within the body between the control port and a bypass restriction passage in fluid communication with the common port; and a control element (316, 318, 350) disposed within the body and adapted for displacement between a closed position in sealing engagement with the supply port to close the supply path, and an open position spaced from the supply port to open the supply path; and characterised in that the control device further comprises: a trim cartridge disposed within the body and defining a plurality of exhaust entry passages of varying dimensions for directing the flow of fluid along the exhaust path when the control element (316, 318, 350) is moved out of sealing engagement and spaced from the exhaust port, the trim cartridge being rotatable between a plurality of positions within the body to define a plurality of distinct exhaust capacities for the exhaust path, and a plurality of exhaust exit passages of varying dimension disposed within the body and in fluid communication with the plurality of exhaust entry passages, such that the exhaust capacity of each of the plurality of positions of the trim cartridge depends on the specific alignment of the plurality of exhaust entry passages in the trim cartridge with the plurality of exhaust exit passages. a body comprising an inlet port, a control port, a common port, and a discharge port; a supply path extending between the inlet port and the common port; an exhaust path extending between the common port and the discharge port; a supply port disposed within the body along the supply path between the inlet port and the common port; an exhaust port disposed within the body along the exhaust path between the common port and the discharge port; a bypass port disposed within the body between the control port and a bypass restriction passage in fluid communication with the common port; and a control element (316, 318, 350) disposed within the body and adapted for displacement between a closed position in sealing engagement with the supply port to close the supply path, and an open position spaced from the supply port to open the supply path; and characterised in that the control device further comprises: a trim cartridge disposed within the body and defining a plurality of exhaust entry passages of varying dimensions for directing the flow of fluid along the exhaust path when the control element (316, 318, 350) is moved out of sealing engagement and spaced from the exhaust port, the trim cartridge being rotatable between a plurality of positions within the body to define a plurality of distinct exhaust capacities for the exhaust path, and a plurality of exhaust exit passages of varying dimension disposed within the body and in fluid communication with the plurality of exhaust entry passages, such that the exhaust capacity of each of the plurality of positions of the trim cartridge depends on the specific alignment of the plurality of exhaust entry passages in the trim cartridge with the plurality of exhaust exit passages. a trim cartridge disposed within the body and defining a plurality of exhaust entry passages of varying dimensions for directing the flow of fluid along the exhaust path when the control element (316, 318, 350) is moved out of sealing engagement and spaced from the exhaust port, the trim cartridge being rotatable between a plurality of positions within the body to define a plurality of distinct exhaust capacities for the exhaust path, and a plurality of exhaust exit passages of varying dimension disposed within the body and in fluid communication with the plurality of exhaust entry passages, such that the exhaust capacity of each of the plurality of positions of the trim cartridge depends on the specific alignment of the plurality of exhaust entry passages in the trim cartridge with the plurality of exhaust exit passages.