Sapphire has the characteristic of high hardness with Mohs hardness 9. With high transmittance, excellent mechanical strength and heat resistance, it can take aerodynamic velocity pressure and heat load, thus is widely used as ultraviolet, visible and infrared windows; also it can be used as the luxury watch cover. Specifications Orientation: C, A, M optional Orientation deviation: < 2º Diameter: Dia5 - Dia 250mm Diameter tolerance: +0 /- 0.02mm Radius of curvature: R10 - ∞ mm Centration: <= 2’ Surface Quality: 40 – 20 Surface accuracy N: <= 2 Irregularity △N: <= 0.5