Nano-Pro X-Treme is specifically engineered for today's competitive recurve bows. When the difference of success can be that of mere millimeters in FITA, NAA and NFAA long-distance field shooting, the Nano-Pro X-Treme is sure to deliver pinpoint accuracy as a result of its multi-spine construction. The Nano-Pro X-Treme recovers faster out of the bow while delivering the flattest trajectory and superior down range accuracy. Keeping true to form of the Nano-Pro series, it has the smallest diameter of any of the Carbon Express target arrows coupled with the parallel shaft design to virtually eliminate cross-wind drift. Straightness: 0.0015", Weight Tolerance: 1.0 grains, Spine Selection Tolerance: 0.002". Available spines: 900 (5.19 gpi) 800 (5.6 gpi), 750 (5.9 gpi), 700 (6.0 gpi), 650 (6.2 gpi), 600 (6.7 gpi), 550 (7.1 gpi), 500 (7.8 gpi), 450 (8.0 gpi), 400 (8.7 gpi), 350 (9.3 gpi).