You have to assume they are all non balanced, just built to factory specs, and then hopefully that.
If someone balanced a set it would be clearly stated (as well as priced accordingly)
Either way, get them balanced before you put them in the truck if your into that, or you'll be thinking about it for roughly 100,000 miles wishing you had.
There have been thousands of injectors installed without balancing that have had no issue. Forum paranoia gets you thinking though...
But, having them balanced by a 3rd party also tests them for proper spray pattern and pop pressure. Having a crappy spraying injector would stink, and you'd probably never know it (hopefully).. Unless it burns a hole in your piston.