Shimano 11-Speed 1.85mm Low Spacer For use on 11-Speed freehub body with 9 or 10-Speed cassette Using 10-Speed cassette on 11-Speed freehub body requires both 1.85mm (FW8991) and 1.0mm (FW4671) spacer Using 9-Speed cassette on 11-Speed freehub body only requires 1.85mm (FW8991) spacer Shimano Cassette Spacers