30 spline, for GM 10.5" 14 Bolt . Uses 1/2" bolts (p/n 14B-RG-KIT1). Manufactured from through hardened 4140 high strength steel. To run 4.56 and numerically higher ratios on this spool you will need thick gears. Manufactured from through hardened 4140 high strength steel. 24.7 lbs. Installation - Service instructions can be found on Service Bulletin #0046.