Voigtlander 20mm F3.5 SL II is a Manual Focus (MF) Wideangle Prime 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 20mm. With a max aperture of f3.5 at 20mm, this is a moderately fast lens.
Voigtlander 20mm F3.5 SL II is not a weather sealed lens, so you have to be extra careful against rain and dust.