Adjustable stop apparatus

An adjustable stop apparatus for limiting movement of an element of a metering valve for setting a flow limit condition of the valve, the apparatus comprising a stop (4), a housing (2), a rotary adjuster device (3) connected to the stop for adjustably positioning the stop relative to the housing, and a guide device (15, 16) operable to guide and secure the adjuster device relative to the housing into any one of a plurality of pre-set positions determined by the guide device.