This is the Hot Racing Helical Spiral Differential Ring/Pinion Gear Set. FEATURES: Fits the front and rear diffs of the following Traxxas vehicles; E-Maxx Revo 3.3 E-Revo Slayer Pro 4x4 T-Maxx 3.3 Summit 4x4 Fits the front diff of the following Traxxas vehicles; Rally VXL Slash 4x4 Telluride 4x4 XO-1 Front Diff High carbon steel construction Helical spiral cut gears provide greater strength and smoother operation than factory bevel cut gears Replaces the Traxxas 5379X gear set INCLUDES: 37-tooth Differential Ring Gear 13-tooth Differential Pinion Gear REQUIRES: Four M2.5 Flat Head Cap Screws High temperature grease COMMENTS: The Hot Racing Outer Differential Case, HRAC1424 is recommended for use with this gear set, and is mandatory if 6-cell battery is used. Shimming may be required for optimal alignment and fit. Check Traxxas manual to verify if model uses the 5379X gear set. Not intended for on road operation if differential is replaced with spool or locker.