The brighter your peep is, the harder it is to see what is beyond it. Does a flashlight shining in your eyes help you see in the dark? No. Only when the flashlight is lighting up your target does it help. Only reflected light off of your target is useful, and fiber optic peeps don't add light to your target. It is a gimmick, pure and simple. It isn't so much that it does not work, it can not work to help you see your target better- all it does is make the peep easier to see. But seeing the peep isn't the issue in low light- seeing the target is the problem.