Are those wheel weights on your rig?
CTIS armor covers.
They're pure unobtainium.
Thousands of sets were made for these trucks but most that ever made it to motor pools were tossed into the trash for some reason (I don't know that I've ever seen a government auction truck with a set actually installed). Some came thru surplus, most likely were scrapped.
You used to be able to buy a set of four for $80. Then they were $80 each, then $100. The last set I saw for sale went for $600.
A few people have tried to make a solution . One of the over-priced scalper sites sells a flat steel ring with only three mounting points that's pretty fugly (might have been a good product with four mounts). Another guy was working with a foundry to make a stamp to punch out the originals. Never heard any follow up, but they aren't being sold anywhere.
There's a few threads on here about the rings. Search for CTIS covers, etc