Abstract: A variable orifice liquid flow meter comprises a body, a bore in the boby defining a flow tube for liquid, a sharp edged orifice in the bore, a piston having a head capable of blocking the orifice and a stem by which the piston is supported for axial movement relative to the orifice, resilient member urging the piston head into a position to block the orifice, support for the piston mounted in the bore, a plurality of fins on the support and extending radially thereof to fix the support to the wall of the flow tube, the support having a generally cylindrical portion formed with a blind bore in which the stem of the piston is slidably mounted and which shields at least a portion of the piston from liquid flow through the bore, the end of the support adjacent to the blind end of the bore being streamlined, a passage in the support permitting communication by liquid in the flow tube with the portion of the piston in the blind bore, and resilient member in the support arranged to urge the piston to block the orif