what offest hitch mount and ball size for aftermarket receiver?

Curious to know what is used by members here. I have an aftermarket 2" receiver and need to get the ball mount and ball for it. I have heard 18" above the roadway and a 2" ball is the most applicable.
 
A 2" ball is pretty standard, unless you have something funky. Of course the ball size can be changed on the hitch mount. As for the hitch mount, I am not aware of a "normal" size. It kind of depends on what you are towing and the height of that. I used my dad's hitch once while towing his trailer and the trailer was level using the CX-9, where as on his truck it is tilted back since his is higher.
 
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