Fitted one of these a while back. Thought this would be the right section for it (NOTE: I use this for night-time possum shooting - but thought that some of you that live in countries where it's not illegal to own a firearm for self defense might be interested!)
For those of you that don't know, they give off a continuous glow by having a tiny sealed vial of Tritium inside a plastic that's coated with phosphorescent material. As the tritium decays (yes, it's a slightly radioactive), the electron strike on the phosphorescent material causes it to glow. Short of smashing the vial open and ingesting it, it can't hurt you.
You don't have to worry about batteries running out. You don't have to leave your gun under a light to 'charge' up the glow. So 24hrs a day, even in your gun safe, your sights are ready to go. Mine came with a 5yr warranty, but are supposed to last for around 12yrs of usable glowtime. And they won't break the bank.
In daylight, the bead looks black with a white centre, and it shows up nicely against the sky, clouds, or trees, or any background i've tried it on.
Sorry for the bad photo's, they don't do the glow justice. On a 23" barrel, even in a pitch black room, i know exactly where my muzzle is.
Just another option for those of you that prefer a shotgun bead to sights. And I'm sure there are Tritium rifle/ghost sights out there for the rest of you as well
