The Carbon Express 52139 Piledriver Cross Bolt is designed for ultimate penetration. The heaviest carbon cross bolt in the CX lineup the Piledriver creates maximum kinetic energy and great knock-down power. Advanced construction ensures spine consistency for great accuracy extremely durable at impact for exceptional reliability and repeat performance. This cross bolt comes fletched with 4-inch vanes. Item Specifications: Straightness: ± 0.004-Inch Diameter: 0.348-Inch. To gain the advantage in the field you need the best equipment which is why so many hunters competitors and enthusiasts insist on the Carbon Express brand.