Yes its for electric trailer brakes. Not just for Dollies but any elec. Brakes. All controllers are wired the same. But I don't see where to plug in this harness, That came in my ford package. I spoke to a friend of mine and he says I can't use the grey plug pigtail because Thor does not offer a place to plug it in.. I have to hard wire it in, but apparently the RV has one blue wire pre run from the back of dash to the 7 pin plug in the back, just need to locate curled up blue wire by steering column. You have Any idea about this????