Pentax D FA 645 25mm F4 is an Auto Focus (AF) Wideangle Prime lens with 645 max sensor coverage. When mounted on a 645 sensor camera, it will give you an FF equivalent focal range of 19.5mm. With a max aperture of f4 at 25mm, this is a moderately fast lens.
Pentax D FA 645 25mm F4 is weather sealed which makes it an ideal lens for outdoor use, especially when coupled with a weather sealed camera body.