The Exotek B6.3 Aluminum Laydown Idler Gear is a hard anodized 7075 alloy 39T idler gear option for Associated B6.3 and B6.2 laydown gear boxes. Must have for high powered racing applications. This is much stronger than the stock plastic idler gear but not indestructible so it is important to use black or white grease on the gears and reapply frequently to prolong its life along with proper slipper adjustments.