Carbon Express 50655 Maxima Blue Streak Arrow with Diamond Weave Carbon Spine and Dual Spine Weight Forward Technology, 350-Sized Black Shaft, 12-Pack Dual Spine Weight Forward technology manages energy better, recover faster, spin 20% sooner, retain more speed and deliver unparalleled accuracy Back shaft section made with patented diamond weave carbon that provides the ultimate in stiffness and unparalleled spine consistency Laser checked for straightness to a remarkable 1/10,000 of an inch; Straightness of +/- 0.0025-inches is a maximum measurement, not an average Items specifications: 350-Size, 8.3-GPI, 0.347-inch Spine and 0.295-inch Diameter 12-pack of black arrows are sorted and matched by weight and spine for best-in-class consistency