Panasonic S Pro 16-35mm F4 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 16 - 35mm. With a max aperture of f4 at 16mm, we can not consider this lens fast on wide end but f4 at 35mm is not too bad for tele end.
Panasonic S Pro 16-35mm F4 is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.