Supporting device for a plastic profile (2), in particular for a plastic pipe, in a calibration device which has a supporting region (1), in which it supports the plastic profile (2), wherein the contour (3) in the supporting region (1) is adapted to the contour of the plastic profile (2). According to the invention, provision is made in that the contour (3) in the supporting region (1), in particular the radius (4), can be changed. Furthermore, the invention relates to a process for changing a supporting region of a supporting device, in which the position of one or more series-arranged supporting devices with continuously changeable supporting region are changed as a function of a predetermined theoretical diameter such that the predetermined diameter is produced.