Carbon braided rails rather than a conventional solid or tubular rail fi39zik39s rails use an outer sleeve of braided carbon fibers forming a tube with the void inside being filled by unidirectional carbon fibers this construction is strong light and stiff wing flex technology wing flex shell has engineered flexibility along the edges where the inner thighs contact the saddle by allowing this area to flex the rider can achieve a full range of leg movement in a wide range of riding