Your welcome to add one to your camera/s or gun/s; and at your own risk and expense of course.
Here's a multi-pic that sort of explains it.
Here's a link to the article: http://www.pointshooting.com/1ahalo.htm
A caution about self defense use:
Scientific investigations and studies of Police combat cases, have established that sights are not used or may not be able to be used in real close quarters life threat situations. As such, one may not be able to use the Halo sight effectively in such a situation, but it's easier and quicker to use than the sights.
So, if you are a sight shooter and have a gun for self defense, learning how to aim and shoot accurately at close distances without using the sights, and to get comfortable shooting that way, makes sense.
And that could get you into taking the next and logical step of learning a method of threat focused shooting.
