Canon TS-E 17mm f4L is a Manual Focus (MF) Perspective Control 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 17mm. With a max aperture of f4 at 17mm, this is a moderately fast lens.
Canon TS-E 17mm f4L is not a weather sealed lens, so you have to be extra careful against rain and dust.