A servo valve comprising: a valve housing; a cavity formed in the valve housing and defining a longitudinal axis; a member disposed in the cavity and axially-moveable therein, wherein the member comprises: first and second sections (32, 34) having first and second cross-sectional areas; a central section located between the first and second sections (32, 34) and having a third cross-sectional area smaller than both the first and second cross-sectional areas; and first and second transition sections (33, 35) respectively between the first and second sections (32, 34) and the central section and forming respective first and second surfaces (33a, 35a) angled relative to the axis, wherein a channel is defined radially between the member and the valve housing, and bounded by the first and second sections (32, 34), the valve housing comprises a plurality of ports (48A, 48B, 48C), each forming a fluid passage through the valve housing in fluid communication with the channel, the plurality of ports (48A, 48B, 48C) comprising first and second ports (48A, 48C) each defining a diameter and having first and second nozzles (50A, 50C) with first and second nozzle openings (52A, 52C) for providing fluid communication between the channel and a spool, the first and second nozzle openings (52A, 52C) each having diameters smaller than the diameter of their respective port (48A, 48C); and a piezoelectric actuator configured to move the member relative to the valve housing, between first and second axial positions, characterised in that: in the first axial position of the member, the second nozzle opening is at least substantially obstructed by the second surface and the first nozzle opening is at least substantially unobstructed by the first surface, and in the second axial position of the member the first nozzle opening is at least substantially obstructed by the first surface and the second nozzle opening is at least substantially unobstructed by the second surface. a valve housing; a cavity formed in the valve housing and defining a longitudinal axis; a member disposed in the cavity and axially-moveable therein, wherein the member comprises: first and second sections (32, 34) having first and second cross-sectional areas; a central section located between the first and second sections (32, 34) and having a third cross-sectional area smaller than both the first and second cross-sectional areas; and first and second transition sections (33, 35) respectively between the first and second sections (32, 34) and the central section and forming respective first and second surfaces (33a, 35a) angled relative to the axis, wherein a channel is defined radially between the member and the valve housing, and bounded by the first and second sections (32, 34), the valve housing comprises a plurality of ports (48A, 48B, 48C), each forming a fluid passage through the valve housing in fluid communication with the channel, the plurality of ports (48A, 48B, 48C) comprising first and second ports (48A, 48C) each defining a diameter and having first and second nozzles (50A, 50C) with first and second nozzle openings (52A, 52C) for providing fluid communication between the channel and a spool, the first and second nozzle openings (52A, 52C) each having diameters smaller than the diameter of their respective port (48A, 48C); and first and second sections (32, 34) having first and second cross-sectional areas; a central section located between the first and second sections (32, 34) and having a third cross-sectional area smaller than both the first and second cross-sectional areas; and first and second transition sections (33, 35) respectively between the first and second sections (32, 34) and the central section and forming respective first and second surfaces (33a, 35a) angled relative to the axis, wherein a channel is defined radially between the member and the valve housing, and bounded by the first and second sections (32, 34), the valve housing comprises a plurality of ports (48A, 48B, 48C), each forming a fluid passage through the valve housing in fluid communication with the channel, the plurality of ports (48A, 48B, 48C) comprising first and second ports (48A, 48C) each defining a diameter and having first and second nozzles (50A, 50C) with first and second nozzle openings (52A, 52C) for providing fluid communication between the channel and a spool, the first and second nozzle openings (52A, 52C) each having diameters smaller than the diameter of their respective port (48A, 48C); and a piezoelectric actuator configured to move the member relative to the valve housing, between first and second axial positions, characterised in that: in the first axial position of the member, the second nozzle opening is at least substantially obstructed by the second surface and the first nozzle opening is at least substantially unobstructed by the first surface, and in the second axial position of the member the first nozzle opening is at least substantially obstructed by the first surface and the second nozzle opening is at least substantially unobstructed by the second surface.