Dyna-frame motorcycles were developed in the 1980s and early 1990s and debuted in the 1991 model year with the FXDB Sturgis offered in limited edition quantities. In 1992 the line continued with the limited edition FXDB Daytona and a production model FXD Super Glide. The new DYNA frame featured big-twin engines and traditional styling. They can be distinguished from the Softail by the traditional coil-over suspension that connects the swingarm to the frame, and from the Sportster by their larger engines. On these models, the transmission also houses the engine's oil reservoir.