Abstract: A fan or compressor stage rotor comprises a disc, radial blades mounted in axial sockets formed in the periphery of the disc, and spacer blocks interposed between the blades to constitute the inner boundary of the air flow path through the rotor. The spacer blocks each comprise an outer wall which is spaced from the periphery of the disc, and front and rear walls extending radially inwardly to overlap at least partially the front and rear faces of the disc. The front and rear walls each comprise at least one hook which co-operates with a corresponding groove provided in the respective face of the disc to fix the spacer block to the disc. The spacer block also comprises a median partition projecting inwards from its outer wall and having a slot through which passes a leaf spring of a vibration damper.