As others mentioned a large gap between the shock skid and the axel shock mount. I added two 1/8" thick washers to fill the gap. Ended up replacing the factory shock mounting bolts with longer ones to provide an adequate amount of thread engagement. No installation instructions. Shock skids themselves are very high quality.

Quality part arrived quickly and install was easy

The skids are made with quality steel, very sturdy and will do the trick. Lack of instructions were offset by the airhead candy in the box!

Fascinated withe high grade quality!

I love the fact that my lower shock towers have an option to be protected now…. These 589 Shock skids are built well! A few improvements could be made however in my opinion:
1) The bolt face hangs well beyond the skid (when tightening it seems as if some holding strength is sacrificed). I’ll try to show in the photo what I mean.
2) There is about a half of an inch (before tightening) that actually bends and tweaks the skid sides inward as the shock bolts are torqued…. I’m not sure if this is a Silverado ZR2 issue, or part of the design. Either way, I like them—and will keep them installed and be happy…