The R.D.R. was a concept derived from PRS competitions. We used it to quickly acquire targets at distance with our scopes still on high magnification. It turns out this is a huge benefit not only to competitors but also hunters. We mounted it on our hunting rifles when we went to New Zealand. While most "hunters" let their ego get in the way of making a decision to purchase something like this we can tell you first hand that it can be a life saver when finding an animal quickly in difficult terrane. You simply put the red to on the target, then look into your optic and there it is. It's just that simple.