Heres a little edumacation for yall about night sights just in case you wanted to know.
Tritium or Hydrogen-3 is a gas element and has a half life of 12 to 12.5 years. The vials in which it is injected into are made of a high strength-breakage resistant Borosilicate glass that is coated with a type of phosphorus powdered solution(different types of phosphors make different colors; green, orange, yellow. I have even seen some blue and red, I think they were made by MMC, and other colors of glow can be purple and white). The radio active Tritium gas emits a beta radiation ray during decay which reacts with different mixtures of phosphors and the result of that reaction is the colored glow you see in the dark.
Also, Tritium is a member of the Hydrogen family of which there is also Deuterium. Hydrogen is the first state of the gas. Deuterium and Tritium are the second and third states respectively. They are also referred to as heavy elements, because they are radioactive. Tritium is also a byproduct of Nuclear Fission in nuclear reactors. Happy Shootin.