Panasonic 20mm F1.7 II ASPH is an Auto Focus (AF) Wideangle Prime lens with FourThirds max sensor coverage. When mounted on a FourThirds sensor camera, it will give you an FF equivalent focal range of 40mm. Providing a max aperture of f1.7 at 20mm, this lens is very fast.
Panasonic 20mm F1.7 II ASPH is not a weather sealed lens, so you have to be extra careful against rain and dust. Panasonic replaced the older Panasonic Lumix G 20mm F1.7 ASPH with this model. Follow the link to read our detailed comparison of these model: Compare Panasonic Lumix G 20mm F1.7 II ASPH vs Panasonic Lumix G 20mm F1.7 ASPH