According to Mac's Webpage:
Totally tech. A tri-system blend of water, emollients and powder. Looks solid, glides on as a soft, creamy emulsion. Provides a natural matte, powder-perfect finish. Smooth to blend, easy to work with: provides a full range of coverage. Water-cooled - refreshes and hydrates skin. Light diffusing: softens lines, creates a fresh, flawless finish. Good on all skin types. Studio Tech is dermatologist tested, ophthalmologist tested, non-acnegenic and safe for contact lens wearers.
This is my all time favorite foundation, it provides full coverage without looking heavy. Although this is my favorite foundation, I don't use it everyday, because the coverage is so good that my skin actually looks impeccable, and I just find that looks fake. I only use it on special days.