How to determine the correct driver bit for screws?
That's basically a #2 PSD2-2 drive. It's designed for relatively high torque driving that would make a normal Phillips drive cam out while minimizing the chance of stripping that you'd have with a square drive.  Wild (and cynical) speculation, but I'm guessing the manufacturer calls it &quot;Unidrive&quot; because Phillips holds a patent on it.  I'd get a #2 PSD2-2 driver (also called Phillips-Square drive, etc.):

Image courtesy of fastenal.com
They're common enough that most of the big-box home improvement stores carry them, but oddly uncommon enough that a lot of the time the screw manufacturer will sometimes include one in the box.