A turbine flow meter comprises a flow pipe which includes an axial through bore and a meter cartridge which is positioned in the through bore. The meter cartridge includes a tubular cartridge housing through which a fluid to be measured is directed and a rotor which is rotatably supported in the cartridge housing. The cartridge housing is slidably received in a first portion of the through bore and comprises an outer diameter which is less than the diameter of that portion of the through bore. The meter cartridge is retained in the through bore by a retainer, which in turn is retained in the through bore by a ring seal.