Actually the "ST" designation is for stickshift. I ran this tires on my 4 speed Stock Eliminator Mustang. These tires have a harder M5 compound, and have stiffer than regular M/T slicks, but not as stiff as a true "stiff" sidewall, which typically carries the "S" designation. Hoosier also has a similar 9" "stickshift" slick with a special compound.