Crossrails
I only paid $90 for the pair from the dealership. They are considered an aftermarket product and GM sold the parts to independent companies. It took three weeks to get. The install was pretty easy - just remove the endcaps and slide these in - they may need some friendly persuasion - used hammer, block of wood and cloth. Took about 30 minutes - would go quicker with two people. I had to run back and forth from side to side up and down a ladder.
These are useful if you haul stuff on top of the roof. Can be adusted front to back, depending where you want them. I did get the black ones.