In 1958 Harley-Davidson took a leap into the modern era with the Duo-Glide, a new frame featuring a rear suspension. The 1957 FLH Panhead was one the last models to have the rigid frame. To compensate for the rough ride Harley offered a spring style seat to provide comfort for the rider. The Panhead was first introduced in 1948 with a 61 and 74 cubic inch version. The name "Panhead" referred to the shape of the pressed aluminum valve covers looking like a pan.