Basically, the trailer hitches you are looking at fit 2 different vehicles. The CURT Trailer Hitch, # 13581, is designed to fit NON-Sport models of the 2011 Mitsubishi Outlander.
If you have a Sport model, you would need CURT Trailer Hitch, # C13079.
The vehicles have different mounting points and dimensions so they require different hitches. I have included a link to the installation details for both hitches for you to view.
With either hitch, I recommend etrailer Ball Mount kit,... view full answer...