Generally the newer faster +310 fps will require you to go one spine stiffer. For instance if you shoot an Easton 340 you may have to go with a Easton 300. The best way to find out is calc the arrow to the bow and then see what it does. When I purchased my Limbsaver DZ-32 it calc'd out to a 340 arrow, but anything past 20 yards and you couldn't hit the broadside of a barn. After several attempts of adjusting the bow, I switched to a 300 shaft and WOW it was right on. I called Easton Arrows and Limbsaver and they confirmed my finding. Easton is supposably writing new software for their shaft selector software to take into consideration of the super fast speeds of the modern compound bow. Good Luck.