Nitro (GPTJ35-4.88) Front and Rear 4.88 Ratio Gear Package Kit Nitro master install kits include: Koyo or OEM Carrier Bearings, Koyo or OEM Pinion Bearings, Pinion Nutif applicable, Pinion Seal, Crush Sleeve or Preload Shims or Solid Spacer Nitro gears are manufactured from 8620 steel gear forgings in the same manufacturing facilities as GM, Dodge, Ford and Toyota Carrier Shimsif applicable, Gasket or Silicone, Loctite, Gear-marking Compound and Applicator Brush They are precision machined using computer controlled processes, heat treated, CNC triple-lapped and Rockwell tested for hardness; these extra steps ensure excellent fitment, ideal contact pattern and smooth, quiet operation