A skinny carbon arrow also has an advantage in increasing penetration in game animals, not just foam targets. When you shoot a live animal, they twist their bodies and contract their muscles, which will ' pinch' the shaft as it passes thru the wound channel. The small diameter shaft will have less surface area to be pinched. If you think that an animal can' t move much by the time an arrow goes thru it, watch some slow motion video of a deer being shot sometime. A dead cow isn' t even a true test for arrow penetration.