Large derailleur pulleys are not the final step to free speed. The Kolossos is now available in an Aero version, so your pulleys and chain are protected from the wind, for riders looking for maximum aerodynamics. The Aero Kolossos is built with Kogel ceramic bearings. The Aero Kolossos is entirely made of CNC machined aluminum with an internal spine for maximum stiffness, helping you cut through the wind and maintain shifting accuracy. When it comes to marginal gains, it simply doesn't make sense to gain a few watts only to give away your advantage every time you shift gears or hit rough asphalt. While the obvious use is for triathlons and time trials, we didn't want to limit the use cases for these cages. The Aero Kolossos is just as at home in road races and criteriums, where the terrain can be bumpy and frequent, aggressive shifting is required. Aerodynamic shape for maximum time savings. Made from CNC machined aluminum. Derailleur pulleys have ceramic bearings.