Tokina 16-28mm f2.8 Pro FX 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 - 28mm. With a max aperture of f2.8, this lens is fast on wide end and equally fast at 28mm with a max aperture of f2.8.
Tokina 16-28mm f2.8 Pro FX is not a weather sealed lens, so you have to be extra careful against rain and dust.