The new 3.9 final drive setup from Central 20 Japan is an economical way of improving acceleration in the 350Z and G35. Increases available power by 10% per gear, resulting in faster acceleration in every gear. These gears really begin to shine with the larger staggered tire setups prevelant in the Z/G world. Professional installation required. Only for use on 6 speed manual transmission models. We also offer an install kit which includes the basic parts needed for installation. This kit is all genuine Nissan parts, and includes pinion Nut, pinion crush sleeve, and pinion oil seal. Call us to order these parts. Please note that in addition to the parts shown, there are also several sizes of side lash adjustment shims that Nissan offers. There is no way for us to determine what size(s) your car might need. The ONLY way to determine the proper size lash adjusters is during the installation by a competant installer. For those with higher mileage cars or who want additional peace of mind during the install, we also can offer the bearings as well as the bolts used internally (called Install Kit 2). Again, these are all genuine Nissan parts. For the ultimate in performance, we also recommend the NISMO finned rear differential cover. This item is special order from japan and can be to you within 2-3 weeks. We ship direct out of Japan or our warehouse when instock. Contact us directly for any questions.