35 Spline 4130 Heat-Treated Moly Material - Extra Strong Maximum Strength & Reduced Rotating Weight Fits 4.10 & Numerically Lower Gear Ratios (3.54, 3.73, 4.10 etc) Provides Complete Lockup of Rearend Dana 60 Chrome-Moly Full Steel Spool - 35 Spline. Full Spools completely replace the standard carrier. They will completely lock both wheels together at all times…Complete Lockup, No Slipping. Not recommended for street applications. Includes 1-Year Warranty Against Manufacturing Defects