I believe the diameter is close to 17/64 or maybe 18/64. Either way, they are made a little heavier than most carbons. A combination of the two allows for better energy transfer from the bow and better penetration. They are advertised as .005 starightness, or .010 total runout. That doesn't chalk up to the .001 some think they need but maybe 100 people in the world can shoot well enough to tell the difference. With the small diameter one should probably use a drop-away rest but they should make a dandy hunting arrow and have mucho durability.