Sigma 19mm F2.8 EX DN is an Auto Focus (AF) Wideangle Prime lens with APS-C / DX max sensor coverage. When mounted on a APS-C / DX sensor camera, it will give you an FF equivalent focal range of 28.5mm. With a max aperture of f2.8, this is a fast lens.
Sigma 19mm F2.8 EX DN is not a weather sealed lens, so you have to be extra careful against rain and dust.