Sigma 50-500mm F4.5-6.3 DG OS HSM is an Auto Focus (AF) SuperZoom 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 50 - 500mm. With the max apertures of only f4.5 at 50mm, and f6.3 at 500mm, the lens is quite slow at both ends.
This lens features on optical image stabilization which helps capturing sharper images at lower shutter speeds. Sigma 50-500mm F4.5-6.3 DG OS HSM is not a weather sealed lens, so you have to be extra careful against rain and dust.