2 5/16 inch hitches are common even on light hybrid trailers. I had a 2750 pound rig with that size. Most trailer companies buy frames that are already made up.
Most hitches have the Ball size requirement stamped right into the hitch assembly. It may have been painted over, but it should be there. As a generality, Trailers over 5000 pounds will go up to the 2 5/16 Ball size, less than 5000 lb may stay with the 2".