I'm not sure what micrometer I need to spec the shims.
Looked around and found many options.

Low end: $16 w/free ship. analog 0-20mm

Utility Micrometer: $20+ship analog 0-25mm
accuracy guaranteed to 0.001"

My fav: Sears Craftsman Micrometer with Wood Case
$99.99 Digital readout reading to .00005in/.001mm

I guess I'll just get the last one, the wood box
has finger joints.