The Sidi Prima is designed for the modern rider. The Prima is easy to wear and adjust, thanks to its Firmor Closure and lightweight upper built to reduce foot fatigue. Its low-profile carbon nylon Aerolite Sole is engineered for efficient power transfer for sprinting, with enough flex and comfort for long rides. -The Single Tecno-3 System creates a perfect balance between the shoe's internal and external side, providing an excellent fit while adapting to every instep -The newly designed integrated heel cup is lightweight and reinforced to avoid deformations after prolonged strenuous use -The Aerolite sole is designed to maximize aerodynamics and power transmission on the bike -The nylon and carbon fiber composite material of the Aerolite Sole provides the perfect balance of stiffness and flex for efficient and comfortable pedaling -Sidi cycling shoes include a replaceable polyurethane heel pad designed for good walkability