It shares this function with the other downstream restrictor, the turbine nozzle.[17] The areas of both the propelling nozzle and turbine nozzle set the mass flow through the engine and the maximum pressure. While both these areas are fixed in many engines (i.e. those with a simple fixed propelling nozzle), others, most notably those with afterburning, have a variable area propelling nozzle. This area variation is necessary to contain the disturbing effect on the engine of the high combustion temperatures in the jet pipe, though the area may also be varied during non-afterburning operation to alter the pumping performance of the compressor at lower thrust settings.[1] For example, if the propelling nozzle were to be removed to convert a turbojet into a turboshaft, the role played by the nozzle area is now taken by the area of the power turbine nozzle guide vanes or stators.[18]