Features:
Hole Jewel contains a series of components that are chiefly applied as supporting bearings to the rotational systems of various accurate chronographs, auto-memorizing apparatus, precise instruments (micrometer, dial indicator) and other apparatus.
Main types: Plane straight/olive holed bearing, single-cup plane straight/olive holed bearing, double-cups plane straight/olive holed bearing, raised olive holed bearing, and single-cup raised olive holed bearing, etc.

Material
Synthetic sapphire/ruby single crystal α-Al2O3, natural agate, spinel, ceramic, etc.