For those who don't know who NOKIAN is: it is a finnish tire manufacturer, owned by Nokia and Bridgestone and other investors. They are the market leader in Skandinavia and have a very good reputation regarding winter tires.
Nokian was also the first company worldwide to offer a winter tire with REAL winter tire capabilities (not just M&S) with an approved top speed of 270 kph instead of the "common" 240 kph for high performance winter tires.

The N0 version of the Nokian WR winter tire for the 997 Turbo has been developed together with Porsche, this tire has a specific mixture of materials adapted to the AWD of the 997 Turbo and the high performance capabilities.
Non N-certified Nokian WR tires are NOT the same thing, even in the same size. Caution!