This lens is an EF 300mm f/4.0L USM.
Features
Diagonal Angle of View: 8° 15' Lens Construction (elements/groups): 8/7 No. of Diaphragm blades: 8 Minimum Aperture: 32 Closest Focusing Distance (m): 2.5 Maximum Magnification (x): 0.13 AF Actuator: USM Filter Diameter (mm): 77
Compact L-series telephoto lens with an Image Stabilizer that compensates for camera shake with the equivalent effect of a shutter speed two stops faster
A more portable 300mm telephoto lens. Two UD-glass elements effectively correct secondary spectrum. Superb resolution and contrast. Astigmatism is also corrected, and background blur is soft and nice. Built-in hood with a locking mechanism.