The ACU-X arrow features a high-performance carbon shaft and a new precision spine-indexing manufacturing technique placing the spine of the arrow in the exact configuration that has been tested and proven to perform best specifically for our rail-less forward draw crossbows, delivering the ultimate in consistency and long-range accuracy out of this platform. The ACU-X Snap-On Nock features our innovative Snap-On design, providing an unmistakable audible click when properly engaged with the bowstring, eliminating lateral nock travel during the shot cycle for precision long-range accuracy, while preserving string center serving life. We ve paired this revolutionary nock with industry-leading 2 Blazer vanes, renowned for their exceptional performance across all archery disciplines, delivering unmatched shot-to-shot consistency at extended ranges. ACU-X 20 arrows feature a 16.5% F.O.C. for improved flight, stability, and accuracy. Each arrow is inspected for straightness to within .001 and each package is weight-grain matched within 1-grain per arrow. Product Specifications Nock : ACU-X Snap-On Nock Length : 20" Weight : 440-grains (+/- 1-grain) (with included 100-grain field point) Straightness : .001" Vane : 2" Blazer F.O.C : 16.5% Insert Weight : 92-grain Brass Insert Inside Diameter : .297 Outside Diameter : .344