What is a SO2 N3 ?

[moto]

I'm trying to buy 2 rears and can only source SO2 N3's. My local dealer says the N3 is speifically for a Porche but another says it's fine for a Griff. Has anyone come across this before or knows if they are OK or not? Any recommendations on where to buy from would be appreciated.

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As far as I am aware they are only for a Porsche, they have a different compound and a slightly different tread pattern. I have been told to not use them.
I have got Dunlop SP9000's on mine, but I don't know what size you are after. Mine are 225/50 ZR 16. Have you tried Black circles?