Replacement gear for Bachmann locomotives. Replaces gear between wheel and gearbox. 18 teeth reduced to 8 teeth. NOTE: When installing gears it is best to put them on a surface and push the axle in from there. They are a tight fit by design and may break if the axle is not installed straight or if gear pressure is uneven. Due to tight tolerances required for proper operation and current manufacturing technique some adjustments may be required of customer to ensure desired operation.