Carbon Express Medallion-XR, Carbon Target Arrow Shaft, Size 600, 12-Pack Straightness: +/- 0.003" Weight tolerance: +/- 1.0 grains Spine selection tolerance: +/- 0.0025" Item specifications: 600-Size, 6.7-GPI, 0.600-inch Spine and 0.239-inch Diameter 12 per pack