Single crystal sapphires are ideal for demanding applications and harsh environments because of their extreme surface hardness, high dielectric constant, and resistance to common chemical acids and alkalis. Sapphire is the second hardest crystal next to diamond, which offers excellent scratch resistance. Sapphire crystal glass has high transparency with a transmission range of 0.15 to 5.5μm.

Shanghai North Optics provides customized sapphire watch windows. Flat and spherical windows and windows of other special shapes are available upon the customer's request.