Tritium H3 watches are the easiest in the world to read in low light conditions and even in total darkness. The light emitting devices require no battery power or any other form of charging, and never need servicing or maintenance. Tritium H3 watches are equipped with a tritium light source. These tiny, airtight vials, sealed under high pressure, are resistant to water, oil and the most corrosive materials. A minute quantity of tritium lights up the dye.