I used it for torquing together a two-piece tungsten guide rod for my 2011 which kept loosening after a couple hundred rounds, even with red Loctite. I couldn't stabilize it to get it tight enough until I used these shims to secure the rod in my vise.
I bought a few of these, and also use them as counterweights in the back of my Ops-Corps base jump helmet when I have my night vision monocular mounted.
Pros: allows great non-abrasive friction hold in vise
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