Anvil and spindle hardened and precision ground — micro-lap finish on measuring faces. Quick and easy zero adjustment. Every thousandth is numbered micro-fine for easy reading. Deluxe heat-insulator on satin chrome finished forged steel frame, tapered for hard to get at places. Disc type anvil and spindle - simplifies measuring thicknesses of difficult, closely spaced sections, ribs, keys, fins, cutting edges on forming tools, chordal thickness of gear teeth, etc. Positive locking clamp. Large diameter, disc will enter inaccessible places such as narrow grooves, slots and recesses over .030" width.