mine are 37 inches and I am 6'3. they are reallly really small... but it's personal preference.
as said above, you should hold the pole upside down just below the basket, and that should place your arm at a 90 degree angle. That's the "correct" size. I wouldn't go any bigger if I were you, but going smaller is personal preference.
based on that rule, mine are like 9 inches too short haha