The tires are zexius xi 326 tires. Purchased at Les Schwab. But they have recommended sipping for other tires I have purchased before as well. Claim better traction on snow due to increases surface area contact, plus longer life due to heat dissipation from the "slits" created. I was very skeptical when told this, and I declined the service. In fact, I too thought there would actually be excessive heat buildup due to additional friction created by the slits.
Thanks to Everyone for your input . . . you have solidified my initial skepticism. Tires are designed/engineered for optimum performance by the manufacturer. It troubles me that a seemingly good company recommends this practice.