This is not listed as an individual part number on any Hornby service sheets, as it is part of the wheel assembly. Gear width or thickness 1.6mm approx.
3D printed final drive gears for EFE - Adams LSWR 02 - EM Gauge conversion
To fit Bachmann class 158 3D printed replacement final drive gears
3D printed replacement final drive gears for Mainline / Replica Peak
Bachmann class 158 3D printed replacement final drive gears
3D printed replacement final drive gears to fit Heljan class 23