RV6 FK8 Upgraded Helical 4th GearOriginally developed for endurance racing teams. The RV6 FK8 helical 4th gear is finally available to the public. We have spent the last 3 years testing and refining the design and materials to take the abuse. These gears feature an extremely strong helical profile with more contact area. The lower tooth count and larger teeth allows these gears to handle more torque and shock load. As most of you know 4th gear is the weak link in the FK8