Designed for elite sprinters, our FuelCell Sigma SD-X includes groundbreaking features to help you feel faster. These unisex racing spikes have a FuelCell midsole that offers a high-rebound feel, designed to promote energy return for sprint distance racing. The full-length Carbon Fiber Plate offers a stiff and responsive underfoot feel with built-in pins for lightweight but powerful traction. Plus, the no-sew construction delivers a sleek fit that helps you feel fast on your feet.