12pc ID4.2 Pure Carbon Arrow Tubes Spine 250 300 350 400 500 600 700 800 1000 Arrow Shafts For Archery DIY Hunting ShootingSPECIFICATIONS Brand Name: NoEnName_Null Origin: Mainland China Type: Bow & Arrow Set Use: Shooting 4. 2 carbon arrow 2)Material : 100% pure carbon 3)Spine: 250 300 350 400 500 600 700 800 900 1000 4)ID: 4. 2mm Spine 400 = 9. 47GPI OD=6. 13mm Spine 500 = 8. 0GPI OD=5. 88mm Spine 600 = 7. 00GPI OD= 5. 8mm Spine 700 = 6. 45GPI OD=5. 6 mm Spine 800 = 6. 2GPI OD= 5. 5mm Spine 900=5. 34GPI OD=5. 36mm Spine 1000=4. 9GPI OD=5. 32mm 6) Arrowheads: 80 grains