07-14 HARLEY FXDWG: Mustang 1-Piece Fastback Seat The Fastback&trade; combines a sleek custom look with soft foam padding and good back support. Although designed for a low, solo ride, these seats can also offer a reasonable degree of passenger comfort.The Fastback offers a super clean, custom style with good back support.Cut low for the rider and tapered in back, the Fastback&#8482; still offers Rear width: 6".