Pirelli Winter Scorpions
Service Center said those were the ones recommended for the X & the only ones they could order thru Parts.
The Nokian Hakka R2's are about the best you can get for traction (from reports, close to the Michelin X-ice) and have the advantage of ultra low rolling resistance. Tesla now recommends these tires, at least here in Canada. Best of both worlds and noticibly better than the Pirelli's I've experienced on loaners a few times in winter over the years.
The Nokian WR-g3 is also low rolling resistance.
We had a national Canadian tire dealer and Nokian rep attend our last Tesla Owners Club meeting and surprisingly, the Nokian guy said he did not recommend the WRG-3 for the Model S or X, only the R2's. I know a few owners with them and speak quite highly, so I'm not sure why he would say that. On the other hand, I've heard of a couple of folks who have had WGR-3 sidewall blowouts on the (heavier) Model X, so maybe they're not as good with the weight of these vehicles???