What is the recomended hitch ball size needed for a class I trailer to pull a small 4 x 6 Uhaul trailer?

[steppinthrax]

I have a hidden hitch Class I trailer. I see at wallmart they sell all different sizes hitch balls? What is the recomened size. Or the size I should get???

 

[bsobel]

The one that matches the trailer which most likely will be a 2"

 

[Zenmervolt]

I believe that 1 7/8" is the standard for a Class I hitch. Checking the U-Haul website shows that their trailers will work with a 1 7/8", 2", or 2 1/8" ball.

ZV