Machined alloy unit that weighs only 3.4gr with the screws. Uses a wider range of available spur gear sizes by Exotek, Kimbrough, etc. Allows for easy switching between a locked spur or the stock slipper as track conditions warrant. Uses the stock top shaft.
Some compatible spur gears:
Kimbrough
Exotek
Also works with Associated B5 based cars and Proline PRO Slash gearbox #6350.