A refiner is disclosed comprising relatively rotatable inner and outer conical refining blades. The refining blades are coaxially arranged around a symmetry axis and are provided with first bars and second bars, respectively, for the grinding of fibrous material. The inner conical refining blade or any of the first bars of the inner conical refining blade extend further along the symmetry axis, in the direction of the tapering of the inner and outer conical refining blades, than the outer conical refining blade or any of the second bars of the counter conical refining blade.