I shoot the older CE 75 out of my Toelke Super D,45#@28 just under 30" arrow length with a 125 gr. point.I think I remember they are around 420 grs..I think the newer 75's have a slightly lighter spine then the older ones.from .608 to .670 spine.I don't use calculator's,I let my tuning determine the length of my carbon arrows.I feel a calculator will get you in the ballpark for an arrow but is only as accurate as the info plugged into it.And then you have the human factor,the one shooting the bow.It's a good arrow for lighter weight bows,mine shoot great and consistent.