Shimano developed the R9100 series mechanical shifting to be it's fastest, most efficient shifting system in the industry. Many details and engineering decisions went into ensuring that would be true. At the same time the R9100 cable actuated brakes got the same treatment so you could get optimal power and control with less lever squeeze and grip power. For both the brake and derailleur cables, Shimano developed a polymer coating for their premium 1.6mm OD stainless steel cable. This was crucial to reduce friction within the cable and housing system.

The Polymer Brake Cable features this coating, which manifests in mini tube-shapes around the stainless cable. This has two major effects. The first is less surface area making contact with the inside sleeve of the housing- which reduces drag in the system. The second is that the cable can curve and bend more easily- again reducing friction. The space between the tubes also holds Shimano's silicone grease better. By refining the lever pivot design, as well as the brake caliper itself, and connecting them with this incredible low-friction cable, the effort to brake has been reduced by about 20%, a massive improvement that you can feel. To maintain the highest quality braking experience with your R9100 and R9150 Dual Control levers and R9100/9110 brake calipers, the Dura-Ace Polymer Brake Cable is the only option.