See detail @ http://www.amazon.com/gp/product/B00009R6X9?&tag=dailymicle-20 An outstanding professional lens for bridging distances in sports, wildlife, and many other applications--including commercial and fashion for the distinct "compressed" telephoto character and totally out-of-focus backgrounds its images can possess. Fluorite and UDglass are combined for incredible image quality, even wide-open. Image Stabilization adds a new dimension in this long lens’ usefulness, even in marginal lighting. It works beautifully with both 1.4x II and 2x II extenders, and now focuses as close as 17.5 feet/5.4 m. It has the same weather-resistant gaskets and sealed focusing and focus pre-set rings as Canon’s other Image Stabilized super-telephoto lenses.