Superior optical performance and agility for professionals:The innovative Sigma 300-600mm F4 Dg Os | Sports combines the power of a prime lens with the freedom to zoom.The Sigma 300-600mm F4 Dg Os | Sports is a revolutionary large-aperture ultra-telephoto zoom lens that delivers all the convenience and versatility of a zoom lens with the superior optical performance of an ultra-telephoto prime lens. With the Sigma 300-600mm F4 Dg Os | Sports, photographers can move freely between focal lengths of 300mm and 600mm without changing lenses.The fast and precise Af performance of its High-response Linear Actuator (Hla) and 5.5 stops of optical stabilization at 600mm make the Sigma 300-600mm F4 Dg Os | Sports a powerful choice for the challenges of sports, action and wildlife photography, where situations change quickly and the opportunity for the perfect photo lasts only a few moments.