Actually I just tried replacing my DS Air Vent bezel using an R170 SLK version. The R170 SLK Series WILL NOT FIT! There are a couple of design changes between the R170 SLK Series & the Crossfire:

1) The outer edge of the Crossfire version is straight. The outer edge of the R170 SLK Series is not; it is angled to the right. If you look closely at the R170 SLK version you will see the left edge of the air vent bezel gets thinner from top to bottom along the louver set.
2) The top of the R170 SLK version is wider to begin with than the Crossfire version. It won't fit the opening in the Crossfire!
3) Another issue between the left air vent bezels is the corner radiis are signiificantly different. The upper corners on the XFire version are smaller radiis than the M-B version.

I was wanting to replace my DS air vent bezel as the labeling is beginning to wear off after years of use & follow-up cleanings during interior detailing. So I'm going to try a couple of alternate approaches to getting the air vent bezel restored. I'll post here with any progress made.