A flow rate device for measuring the flow rate of a fluid flowing through a wellbore is disclosed. The flow rate device includes a differential pressure conduit, a flow restrictor insert and a differential pressure measurement device. The differential pressure conduit is locatable in the wellbore, defines an internal bore, and is adapted to include a restriction having a cross-sectional area to increase the velocity of fluid flowing through the differential pressure conduit to create a differential pressure. The differential pressure conduit defining first and second pressure measuring stations axially spaced along the differential pressure conduit. The flow restrictor insert is located in the restriction to reduce the cross-sectional area of the restriction. The flow restrictor insert defines an internal bore having a cross-sectional area less than the cross-sectional area of the restriction. The flow restrictor insert also has a pressure measuring port aligned with the second pressure measuring station. The differential pressure measurement device has at least one pressure sensor for detecting the pressure at the first pressure station, and for detecting the pressure at the second pressure station to generate a signal indicative of the flow rate of the fluid.