The Extang Tuff Tonno truck bed cover features smooth edges with a tarp-tightening rotating tail rail and spring loaded bows. The Tuff Tonno's rotating rear rail is Extang engineered to offer a better looking truck bed cover that is easy to use. SpringLock bows are simple to install and they wont fall off at any speed. Get a clean, smooth look with the worlds strongest tarp attachment system. The Tuff Tonno even set a world speed record at Indy and now holds a place in the Indy Hall of Fame!