Abstract: A flowmeter having a flow passageway with co-axial inlet and outlet openings at its opposite ends and a vaned flow measuring rotor between the openings. The rotor is mounted in low friction bearings and yet the meter is operable within the normal accuracy specification for a conventional high-friction meter as a result of the presence of a constriction in the passageway upstream of the rotor. The passageway and constriction are of circular cross section and the constriction has a main portion which opens directly at the downstream end near the rotor, and a tapering upstream portion connecting with the passageway. The constriction affects flow at the rotor at turbulent but not at laminar velocities.