Don't know what it is, but they did not last for me. I genuinely liked the tires, just could not afford them. I had forgot the Car and Driver Link which helped with my decision to switch.

Since my Eurocharged tune and Sprint Booster additions, the rears are definitely getting roasted (though a little less now with the Hankooks). The one good thing about the Hankooks is that they even spin from a stop quietly. If I apply a little extra pressure to the go pedal, it lights them up. Almost no noise or smoke. Just an odd sensation of the rear slipping a bit and moving to the right, then BAM! it is like being launched by a cannon as it changes from slip 'n' slide to slingshot...LOL