Thats Hoyt's tune charts. Spiral Cam & 1/2 would be the fastest cam. You'll need to call Hoyt Customer Service and find out what limb deflection you'll need to get your desired lbs. So you'll need to tell them what year your bow is (they could probably run the serial number if you don'y know), what limbs (XT-2000, XT-3000, etc, etc) and what the deflection numbers are on the limbs you have now. 801-363-2990 Good luck.