Small Hole Gages -- Series 829, 830, 831 (Starrett) Hardened ball measuring surface with two-point contact. Smooth, sensitive size adjustment. The contact surface consists of a split ball that is adjusted to size by a knurled knob at the head of the gage. Final size thousandths of an inch is obtained by measuring over the ball contacts with a micrometer. Made in USA and ISO certified.
