A full line of highly spherical sapphire and ruby balls with precise surface finishes for applications requiring superior hardness and chemical resistance are available from Meller Optics, Inc. of Providence, RI. Meller Sapphire and Ruby Balls feature Mohs 9 hardness which is second only to diamond and are impervious to most chemicals, solvents and detergents. Offered in a wide range of sizes, they are suitable for applications such as ball check valves, chromatography pistons and pumps, jewel bearings in time pieces, stylus tips, and fiberoptic and endoscope lens assemblies. Supplied with a calibration certificate validating diameter and sphericity, Meller Sapphire and Ruby Balls are available in 42 inch and metric sizes from 0.1 mm to 0.5” dia. and have surface finishes of 0.008 to 0.010 micron Ra. They have a 0.2 coefficient-of-friction, a refraction index of 1.76 microns at 20°C, and 2,000°C melting point. Meller Sapphire and Ruby Balls are priced according to material, size, and quantity; delivered from stock. Samples and price quotations are available upon request.