I love this site - TruGlo TG131AR Tritium Fiber Optic AR-15 Sight

This is really a very underrated site. They are a pain to put in I will give you that and they are a bit of a hassle to adjust. But having said that once you are done you cant beat them. They glow in the dark due to their tritium light source and are exceptionally bright in daylight conditions. You get this lovely green dot that changes intensity depending on how sunny it is. So on an overcast day it is the right level of glow and on a sunny day it is the right level of glow. At night it just barely glows. The thing is great! The only negative thing I have say about it is that they are potentially a bit fragile. But they are very well protected by the site post so unless somehow you manage to drag the fiber optic trough the dirt I am not sure how you could damage it. So unless you are in low crawling through the jungle I really dont see an issue.