This lens is included fisheye function 180 degree at 10mm and ultra wide 100 degrees at 17mm. Sure, there is lots of distortion in 10mm because it is fisheye, but it is not a bad point you cab create many creative photo from it. At 17mm, you can take 100 degree with just a few distortion.
Both fisheye and ultra wide in the same lens; good build quality
Cannot install filter; an unique design of lens cap if lost it have to pay much for it