Flip card placards for flatbed

Hey everyone,
I was wondering what Flip Card is best for a flatbed or Stepdeck. They have Different kinds like the 15 card, 10, 8, 6. I noticed that the 15 card does not have any class one on it. I’m mostly wondering what is the most common types of placards used on a flatbed or Stepdeck. I planned on doing two on each side of the trailer one Flip card style and one holder in case it was something specific. Or would it be smart to just do two holders on each side?

 

I recently got my HME and haven’t moved anything yet so I guess it’ll depend on what is needing to be shipped. I’d just rather be prepared and not searching for more placard holders last minute before I get loaded.