What is Trit short for, where do we buy it?
Trit is short for Tritium, which is a radioactive form of hydrogen gas. Its radioactivity is extremely weak, it doesn't even register on standard detecting equipment, however if you put some of it in a sealed vial with some phosphor, it's just powerful enough to cause the phosphor to glow. Since Tritium has a radioactive half-life of 12 years, that means the now-glowing vial will glow nonstop for many years! It's like a halloween glow stick that never dies, or glow in the dark material that never needs any light or charging. If you put one of these vials on your flashlight, you'll be able to quickly and easily find your flashlight in complete darkness, even years from now, with no maintenance of any kind needed on the vial.
You can find many different shapes, sizes, and colors of tritium available on the CPF Marketplace. The tritium vial I use on my Fenix P1D pictured above is a Merkava DIY II Glowring (
http://www.cpfmarketplace.com/mp/showthread.php?t=182082), a vial in a high-impact tube that's then put on a keyring - anything that accepts a keyring, I can now have a tritium vial on, very handy!