Each pair of fins is built to order, there are no fibre fins available with this level of flexibility on the tip and stiffness on the blade, giving power and efficiency. You choose the level of stiffness, and can choose a differing shape, for example thinner. Their outer laminate is a high tenacity fibre, and the core carbon fibre, I only use the highest specification material available, breaking them is a yet unfulfilled challenge. However should they break, there will not be a sharp edge, as the carbon is encased in the high tenacity fibre..