Easton RX7-21 525 spine Carbon Shafts - 12 Pack - Easton's new RX-7 series 7178 aluminum arrow shafts incorporate a precision rear taper - effectively letting recurve shooters shoot a bigger arrow at a lower bow weight, and also with less point weight, while maintaining maximum shaft diameter for higher scoring potential. This design element drops the dynamic spine of the arrow shaft by up to one full size, which allows the use of a larger diameter and lighter point. Straightness: +/- .001in Weight Tolerance: +/- 0.75%