Mithras:
Emperor:
The ones on the Turbo almost look like 18s to me while the 4S is rocking 19 inch ones. Could be wrong though as the car dwarf any rims under 20 inches. 

The turbo is pictured with 19's (for some strange reason) but will come with 20's as standard and 21's as an option. 19's will be standard for the NA V8 and maybe 18's for the V6 but I think just a different 19.
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Past-President, Porsche Club of America - Upper Canada Region
Thanks. The roads in the US can be quite rough which makes 19 inch rims reasonable for comfortable journeys. Entry level S-class and 7-series also come with tiny "tiny" rims.