35 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. 24.7 lbs. Installation - Service instructions can be found on Service Bulletin #0046.