Features - SH-RC903 Wide Lightweight and breathable microfiber leather provides optimal fit and premium comfort for the entire ride Premium heel counter with anti-twist protection for optimal foot positioning during hard acceleration Slim, low-profile cross lacing provides elegant forefoot lockdown Two low-profile BOA Li2 twist locks for quick and precise fine adjustment Integrated seamless midsole and upper construction for unparalleled fit, stability and lightness Adjustable Powerzone wire guide for reliable forefoot support Stiffness index: 12 out of 12 Weight: approx. 450 g in size 42 (pair) Pedal recommendation: PD-R9100 Technology SPD SL SPD-SL pedal system provides a seamless connection between shoe and pedal for more effective power transfer under extreme pedal loads with wide cleat design for stability while pedaling and walking. SHIMANO DYNALAST The toe spring area of a cycling shoe plays an essential role in supporting pedaling efficiency. If it is too high, it can cause more tension in the plantar, calf and posterior thigh muscles. If it is too low, it results in a flexed, inefficient pedaling motion. Extensive research by R&D experts at Shimano has resulted in a superior shoe last design with an optimized toe spring area that promotes a smoother, more energy-efficient upward motion. Shimano Dynalast was developed based on feedback from pro riders and helps reduce energy loss on long rides. So you have more power for the final sprint across the finish line. Limit energy loss through greater pedaling efficiency: between crank angles of 200 ° and 360 ° occurs in the backward phase of a pedal movement a loss of power or energy. Shoes that use Shimano Dynalast help reduce this energy loss by supporting a smoother, more efficient pedaling motion. If you want to reduce fatigue, get the most out of your legs, or simply perform a bit better, you should ride with Shimano Dynalast.