This has been discussed on many of the xbow forums I frequent. My opinion, not needed, more trouble than it's worth. All you have to do is take a shot at 10 yds, hopefully you are on the target, then go to 20, 30, or whatever. I've rarely adjusted a scope from 10 yd poi, don't use red dots, but it's the same principle. I'll also go out on a limb here and say that the real problems w/ a set up don't start to show up til 30 yds.