This International Standard specifies the dimensions of surfaces on which servovalves are mounted in order to ensure interchangeability. It applies primarily to electrohydraulic flow-control servovalves which represent current industrial practice. It is applicable to four-port servovalves and also to five-port types, i.e. those in which the pilot stage is supplied with hydraulic fluid separately from the remaining stages. In addition, this International Standard may be used for pressure-control servovalves. If the valve is used in a three-port application, either service port (A and B) may be omitted. Because there is no clear distinction between servovalves and certain proportional control valves in performance and/or application, the existence of this mounting surface for servovalves does not exclude the use of a mounting surface as specified in ISO 4401.