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 3 minutes in the bike leg of the Ironman Triathlon! No wonder Keith Bontrager himself calls the R4, "the World's Fastest Tire."