Meller Optics Inc. can custom-fabricate sapphire optics that are impervious to most acids, alkalis and harsh chemicals to approximately 350 °C, making them suitable for use in hostile environments. They can be windows from 0.5 to 9.5 in. in diameter or domes and lenses from 1 to 4 in. in diameter. The optics, with a Moh 9 hardness, transmit from the UV to IR and provide up to 85 percent transmission uncoated and up to 99 percent with antireflection coatings on two sides.