From Exotek Racing:
Ultra light weight center spool set for the EB410. Greatly reduces the rotating mass of your XB4 for that extra boost in 13.5t and 17.5t spec racing. The Exotek spool set weighs 18gr with the spur gear and the included coated hard steel outdrive cups.
Machined 72t pom spur gear is included and bolts on to the lightweight alloy spool.
For non-boosted 13.5 or 17.5 classes only.
Also compatible with Exotek spur gears or standard 48p Kimbrough spur gears #144 , #145, etc.
NOTE: MUST USE ANTI WEAR GREASE FOR THE STEEL CUP AND BONES.