3-Speed disc brake internally geared hub with a wide gear ratio of 177% Rotary gear selector without protrusions outside the frame 6061 Aluminium hub shell Compatible with 17 to 19 teeth sprocket Anodized finish RR 3s Int 36H B/O 3/8 Alloy Sil 1095g 6B 135mmUPC/EAN/GTIN: 4710944257588