Diamond Impregnated, Needle Files
Incredibly hard, industrial diamond, powder impregnated surface requires very little travel to quickly cut even the hardest materials - carbide, steel, glass or ceramics.
Big Book Catalog, Issue:68, Page:477
SPECS: Available in either Coarse or Fine grit. Files are 5.5"
(14cm) long. Carbon steel shanks are .118" (3mm) dia.