Pictures of tow vehicles and trailers

You need a 2 inch ball. It needs to have a rating at least as high as the heaviest trailer you want to tow, higher than needed doesn't hurt anything. 

The nut needs to be tightened to 250 ft-lbs. which is a lot. They are notorious for getting loose if not torqued properly. So either you need to have it put on your Blue Ox at a shop or you can slide the hitch into the receiver sideways, put your box wrench on the nut, and carefully put your full weight on it. If you weigh 250 lbs stand 1 ft away from the nut, if you weigh 125 then 2 feet, 187 lbs then 1.5 ft, etc.  Its OK to go over a little. 

Also, visually checking the ball for tightness should be part of your pre-tow checklist every time you hitch up. 

 
 

I purchased it at an auction last fall and this is our first season with it...if I recall, there was some confusion when I went to register it as the bill of sale had "2010" on it, though it's a 2011 model year....the person who wrote the bill up (at the auction house) was confused over the VIN #.