The main benefits of the hollow carbon construction are simple: Stiffness & weight savings. Youll also feel zero crank flex. Fitted to the arms are a pair of Semi solid AL7075 100% CNC process chainrings secured by AL7075 Torx T-30 alloy chainring bolts. The SL-K uses a Mega Exo bottom bracket which is built with hardened steel ball bearings instead of the ceramic hybrid bearings of the K-Force Light, this helps reduce the cost of the overall system but allows for an upgrade to the Ceramic version at a later date. Q-factor remains narrow at 145mm & a chainline of 44mm means smooth shifting with 9 or 10 speed Sram, Shimano drivetrains.