Original sentence: The FXST designation is used when the X-type fork is used or when the Springer fork is used with a 21" wheel, while the FLST designation is used when the FL-type fork is used or when the Springer fork is used with a 16" wheel.The word softail is a registered trademark of Harley-Davidson motorcycles coined with the release of the FXST Softail in 1984.These motorcycles have the same engine, transmission and frame with the exception of the Deuce, which has a 2" backbone stretch, but differ in the choice of fork, wheels and accessories.designed the softail in the early '70s
Edited sentence: The FXST designation is used when the X-type fork is used or when the Springer fork is used with a 21 inch wheel, while the FLST designation is used when the FL-type fork is used or when the Springer fork is used with a 16 inch wheel.The word softail is a registered trademark of Harley-Davidson motorcycles, coined with the release of the FXST Softail in 1984.These motorcycles have the same engine, transmission and frame with the exception of the Deuce, which has a  backbone stretch, but differ in the choice of fork, wheels and accessories.designed the softail in the early 1970s