Fowler Disc Micrometers simplify measuring thickness of difficult, closely spaced sections, ribs, keys, fins, cutting edges on forming tools, chordal thickness of gear teeth and more. The extra large diameter disc will enter normally inaccessible places such as narrow grooves, slots and recesses.Hamm ertone blue baked enamel frame is tapered for hard-to-get-at places.Anvil and spindle are hardened and precision ground with microlap finish on measuring faces.Positive lever locking clamp.Quick and easy zero adjustment on sleeveRatchet thimble for repeatability.Meets or exceeds Federal accuracy specs.Sizes over 1" include standardsIncludes case.