Installed these on a 2011 Sierra. The fit is not perfect, however if you use some self tapping screws instead of the holes provided and adjust the position of the flare you can get an acceptable fit. They do not fit tight to the body without adjustment.
This product is ok, but i would never buy it again. The fronts fit just fine. The rears on the other hand are a real pain. The profile to the body is off and I had to use a clamp to get them on!