Not too bad, pretty easy. I drilled an extra hole on each side, because I didn't want to use the glue that was included. The extra hole is 'extra' on the splitter, but not on the bumper cover. I matched the hole on the bumper cover to the splitter. I also cut off the "ears" on each side of the splitter, so that I did not have to remove or modify any of the OE plastics on a US Spec FiST. Other than that everything else lined up and fit as you can see in the photos. I've included pics below to try to help describe.