RZR 800 has a 1 -1/4" receiver hitch. The U-4047 is a 2" so you'll need to check out the U-4063. Just enter that part number in the search bar.
You will want to measure the distance from the center of your receiver hitch pin hole to the point behind your bumper or bed and compare it to the dimensions on the U-4063 so you can confirm it will clear the back of your RZR