Features: Balls & balls measuring head jewels are made of synthetic sapphire/ruby. They are largely used in heavily corrosive environment and optical fiber communication because of its anticorrosion, wearable and fine transmission characteristics. Balls measuring head jewels are used as insulated measure head on precise instruments. Material:sapphire/ruby , natural agate, SiC, ceramic, crystallite glass ,Si3N4 ,spinel, hard alloy etc.