A bladed disc comprising a disc hub 110; a set of blades 120 angularly distributed around the disc hub; wherein there is variation in a geometric parameter between the blades. The blades are positioned around the disc hub such that for a majority of pairs of neighbouring blades in the set, an interval between values of the geometric parameter between the blades of the pair is less than 0.5 standard deviations of the geometric parameter for the set of blades.