Bontrager's R4 Aero Tire is all about making you faster and more efficient. Its 220tpi casing creates less drag and provides a supple road feel you'll love, while the tread minimizes rolling resistance and grips great in the corners. The R4 Aero also features integrated flat-tire protection. Plus, this amazing tire has Bontrager's unique aero wing design that saves you energy mile after mile. In fact, it has been tested to save over three minutes in the bike leg of the Ironman Triathlon! No wonder Keith Bontrager himself calls the R4, "the World's Fastest Tire."