Springers were offered, that looked like the 1936 to 1948 Knuckleheads. There have been many Harley-Davidson models with the Softail frame, including the Softail Standard, Custom, Springer Softail, Heritage Softail, Heritage Springer, Night Train, Deluxe, Deuce, Fat Boy, Softail Slim, the Dark Custom Cross Bones, the Dark Custom Blackline and Breakout. With the exception of the Deuce, which has a longer tank, these motorcycles have the same engines, transmissions, and frames, differing mainly in the fork, wheels, and accessories. Front forks The Softail model line has multiple front fork configurations. Historically, they have had Springer leading link forks, reminiscent of the sprung front-ends that were used before the Hydra-Glide in 1949. The FXST designation is used for 21" front wheel bikes or when the Springer fork is used with a 21" wheel, while the FLST designation is used for 16" front wheel bikes or when the Springer fork is used with a 16" wheel. Engines Because Softail models do not have rubber-mounted engines, they have more vibration in Evolution-engined Softails than in rubber-mounted Touring or Dyna models with Evolution engines. To compensate, later models used a counterbalanced version of the Twin Cam engine, the 88B, instead of the regular Twin Cam engine used in the Touring and Dyna models. The Twin Cam was enlarged to 96Bb and 103B before it was replaced by a variant of the Harley-Davidson Milwaukee-Eight engine for the 2018 model year. New Softail from 2018 onwards In 2017, Harley unveiled a completely redesigned Softail frame for the 2018 model year, the first major change since the introduction of the Twin Cam engine in 2000. The 2018 Softail frame uses a differently shaped swingarm suspended by a single rear shock absorber, mounted underneath the seat in a similar fashion to the original Haubert and Davis designs. Harley claims that the new chassis is significantly stiffer and lighter than the previous-generation Softail and Dyna platforms, the latter being discontinued with some of its models being carried over to the new Softail chassis. The 2017 Street Bob 103 ci was dyno tested and made and at the rear wheel. The new 2018 Street Bob 107 ci makes and at the rear wheel. The 114 ci motor such as in the 2018 Heritage Classic produces and at the rear wheel. Customizing The Softail is the most popular Harley-Davidson model family for heavy customizing and is often used for show bikes.