If you’ve ever stripped the gears on a BLS251 and look for the advertised replacement gearset you’ll notice that the advertised BLS251 gear-set come with the one metal output gear and are certainly not cheap. Because of so many plastic gears it’s highly unlikely that the metal output gear will get damaged. What you might not know is that the BLS251 and BLS256HV share plastic gears with the S9251 and S9256. You can purchase Futaba part# FUTM3502. This is a 5-pack of all three gears needed for about $12. – Nick