This gear fits on the Layshaft of 5-speed Hewland and Webster Mk-series and Formula Mazda gearboxes (except Mk5). Hewland part number HC9-238.
Four-speed gearboxes can use this gear with the addition of the 4-Speed Reverse Driver Gear Spacer, Part No. 1410-A59-1 (sold separately). The spacer makes up the gap left by removing 1st gear from the 5-speed stack.