This is the Nismo S-tune exhaust, which is slightly different from the Nismo factory exhaust. The S-tune is available as a dealer accessory or can be purcahsd through any of the larger vendors (i.e. Motorsport).
Nismo S-tune Exhaust
I have this axle back and modified the flanges to allow it to bolt up to the Nismo factory H-pipe. Great combo IMHO as I like the exhaust tips on the S-tune better than the factory Nismo tips.
Considering the cost to buy it new, this is a great deal.
My $0.02.
Dave N.