Abstract: An apparatus for screening a fibrous suspension including: a housing, conduits therein at least for fiber suspension being fed, reject and accept, and a rotor and a cylindrical screen drum installed in the housing, at least one of which is rotatable, whereby a surface of the rotor is provided with rotor elements in proximity to the surface of the screen drum, whereby each rotor element includes a front surface facing a flow of the fiber suspension, an upper surface and a trailing surface sloping from the upper surface towards the surface of the rotor, wherein the trailing surface of the rotor element is curved and sidewalls of the trailing surface converge at a back point of the rotor element.