An adjustable sizing device for sizing extruded continuous profiles, in particular tubes, includes a plurality of segment bodies disposed about a circle and having a plurality of slats for defining with their radially inner ends a common sizing opening. The segment bodies are held and adjusted in radial direction by actuators to thereby allow change in dimension of the sizing opening, wherein each of the segment bodies is operatively connected to at least one of the actuators. The actuators are received and aligned in at least one mounting ring which has a number of radial bores spaced from one another in circumferential direction at a number corresponding to a number of segment bodies.