2008 Ultra classic electraglide need to replace rear hydraulic switch which is behind exhaust pipe, what size of wrench is used it's between a 1" and 1 1/8" but sure it's metric like most everything else these days.

 

Replaced the one on my 07 a year ago. It's the same switch but I don't remember the size. I think I just pulled wires and tried different sockets til I found one that fit.
You could always buy a new switch and fit it that way. You'll need the new one at hand anyway when you pull the old so you don't lose a lot of fluid.
Be sure to bleed the brakes after the swap. Some will tell you you dont have to if you're fast with the swap but don't believe that. Buy a speed bleeder for the caliper when you buy the switch. Makes bleeding very quick and easy.

 

If it's between 1" and 1 1/8" that would make it 1 1/16"