Knurled knob at the end of handle is used for size adjustment
Hole size is obtained by measuring over the contact points with a micrometer
The gaging surface is a full-round with a flat bottom
This permits use in the smallest of shallow holes, slots and grooves, etc.
Gaging surface is fully hardened to ensure long tool life
Extra long for gaging deep and shallow slots and similar work. The complete set of four gages covers a range of .125" - .500". Includes fitted vinyl case.