Provides Complete Lockup of Rearend 4130 Heat-Treated Moly Material - Extra Strong Scalloped Design Provides Maximum Strength & Reduced Rotating Weight Fits 3.92 & Numerically Higher Gear Ratios (4.10, 4.56, 4.88, etc) Dana 44 Chrome-Moly Full Steel Spool - 30 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 applicatons. Includes 1-Year Warranty Against Manufacturing Defects