The XB4 gear diff ensures increased on-power steering for nearly all types of tracks, and is ideal for both carpet and clay tracks. The super-smooth gear diff includes a composite case and cover with exchangeable spur gear. The gear diff set includes 81T spur gear and a range of various spur gears is available as an option.The internal gears are precision-molded from tough XRAY developed composite material, ensuring long lifespan and super-smooth, efficient operation.The maintenance-free diff design will benefit racers of all levels. When the diff is correctly built, there is no need for maintenance for a very long time no need for frequent oil changes, and no leakage due to our superior sealing system.Parts list:#304930 Composite Gear Differential Bevel & Satellite Gears (2+4) #304980 Composite Gear Diff Cross Pin #304990 Gear Diff. Gasket (4) #364910 Composite Gear Differential Case #364911 Composite Center Gear Differential Adapter #364970 Center Diff Outdrive Adapter - HUDY Spring Steel (2) #364981 Composite Center Diff Spur Gear 81T / 48 #903258 Hex Screw SFH M2.5x8 (10) #902306 Hex Screw SH M3x6 (10) #964031 Washer S 3.5x10x0.2 (10) #964050 Washer S 5x15x0.3 (10) #972050 Silicone O-Ring 5x2 (10) Note: The diff gear will not fit XB4, XB4'14 and XB4 2WD due the different length of the drive shafts.