From the manufacturer's official website:

Proven in the Tour de France peloton, the distinctive looking Pro Race™ road racing tire marks the next generation in road racing clincher technology.

THE CASING: The Pro Race™ road racing tire features a special casing which is remarkably supple, yielding a road feel that rivals fine tubulars. It utilizes our special polyamide casing plies, plus a high density interwoven nylon belt under the tread. The result is a supple ride and high rolling efficiency, plus enhanced puncture resistance in the tread area. The belt is also designed to reduce casing stretch caused by high pressures, thus increasing tread life.

THE TREAD: The Pro Race™ racing tire uses two low rolling resistance Silicium™ tread compounds that have been refined by Michelin engineers for resistance to small cuts and enhanced grip.

THE PROOF: Ridden to over 300 professional road victories, including nine Tour de France stage wins and the green points jersey in both 2002 and 2003, the Michelin Pro racing tire family is quickly changing the look of pelotons all over the world.