Abstract: A flow meter for use in an oil well has a central bore region in which an annular tube is fixed co-axially with the central bore region by a ring, which also seals the gap between the inner bore of the central bore region and the tube at its downstream end, thus forming a pocket open to the direction of fluid flow through the central bore region. The pocket brings the fluid to rest, thereby converting all of the dynamic pressure of the fluid into static pressure. This has the effect of maximizing the pressure differential obtainable between the central bore region and a position upstream of the tube, which allows an electronic calculation to be made to provide a more accurate flow rate measurement than would have been possible without the pocket.