Comparable to a single focal length lens, it has four UD-glass elements to correct chromatic aberrations. Its constant f/2.8 maximum aperture and superb image quality make it one of the most popular professional SLR lenses in the world! Features for the Canon EF 70-200MM f/2.8L USM Telephoto SLR Lens include:*w/Case LZ1324 and Hood ET-83II*Compatible with Extender EF 1.4x II and 2x II. *UD lens. *Ultrasonic. *4 UD Glass. *Inner/Rear Focusing.*Full-Time Manual Focusing.