Sigma 24-35mm F2 DG HSM A 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 24 - 35mm. Providing a max aperture of f2 at 24mm, this lens is remarkably fast on wide end. Even better, having an aperture of f2 on tele end, this lens is exceptionally fast through out its range.
Sigma 24-35mm F2 DG HSM A is not a weather sealed lens, so you have to be extra careful against rain and dust.