When efficiency AND aerodynamics are critical, our AERO System is the top choice for many!  Utilizing a 14-Tooth / 18-Tooth pulley wheel combination, the AERO System is unmatched by any competitor on the market when it comes to strength, durability, performance, and aerodynamics!  Reducing drivetrain friction and aerodynamics does not have to come with a trade-off of decreased durability, decreased shifting performance, or even taking an aesthetic step backwards (current offerings on the market).  SLF Motion Oversize Systems use cages produced from "Made In The USA" 100% real carbon fiber (unlike competing brands' nylon plastic "composite" cages) along with unique coated bearings for added durability and performance.  Improve your current stock drivetrain or even your current competing Oversize System with the installation of an SLF Motion AERO System.  Every System is designed, tested, and hand built in Pawnee, Illinois USA.