Abstract: A modular apparatus for cooling and sizing extruded plastic profiles includes a base plate and a first side plate which are permanently connected together and perpendicular to each other so as form a pair of reference planes. One or two groups of vacuum sizer die elements having a passageway through which an extruded plastic profile will be advanced forwardly in a longitudinal direction from an extrusion die, are placed onto the reference planes. Each of the vacuum sizer die elements has reference surfaces which mate to the reference planes; and the group or groups of vacuum sizer die elements are secured in place in the apparatus with one or two further side plates and a top plate. Vacuum is provided to the vacuum sizer die elements through vacuum connections arranged in the base plate, and cooling is provided in a cooling water passageway formed generally in the side plate.