[rosatelg]

They are 100% directional, see the image below from the Chevy installation instructions. The dealer confirmed as well. I can't talk to other brands/models/makes but in my case, after the job was done, things were good for 500 miles, then I started to feel a little shimmy coming from the front end. I was due for tires so I ordered the new set and had them installed and a wheel alignment done. The next 500 miles the shimmy got a little worse. Finally in the next 500 miles the brake pulsing started.

Looking back I saw how the improperly installed setup started to show signs of failure. The fact that these monster rotors warped in 1500 miles of driving says a lot.

The comment on keeping the parts is spot on. Had that issue before and they will not release warrantied parts. I have marked my rotors to assure that very thing does not happen.