Canon 16-35mm f4L IS USM is an Auto Focus (AF) Wideangle Zoom lens with 35mm FF max sensor coverage. When mounted on a 35mm FF sensor camera, it will give you an FF equivalent focal range of 16 - 16mm. With a max aperture of f4 at 16mm, this is a moderately fast lens.
This lens features on optical image stabilization which helps capturing sharper images at lower shutter speeds. Canon 16-35mm f4L IS USM is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.