Carbon Express Nano-Pro RZ Shafts 600 1 doz.. Parallel designed shaft has three different spines with a more flexible center Red Zone and stiffer front and back sections. This manages how an arrow flexes in flight to deliver pinpoint accuracy. Will not take a set like aluminum core arrows and will maintain initial spine for several seasons. Straightness tolerance: +-.0015" Weight tolerance: +- 1 gr. Available in sizes 400 (8.7 GPI) 450 (8.1 GPI) 500 (7.6 GPI) 550 (7.2 GPI) 600 (6.9 GPI). All components sold separately. Package Contents: Carbon Express Nano-Pro RZ Carbon Express 51591: Nano-Pro RZ Shafts 600 1 doz.