I use the top of the stadia arcs, where they hit the insert ring, as my 10 yd reference. I tested it at distance and every weight arrow I have, it works every time with the correct speed insert. The ring for every speed has the same 20 yd mark, so in theory, shooting 20 yards or less, it doesn't matter what insert you use if you zero on the 20 mark and don't shoot beyond that.