Randy.....The speed 12 is higher down force body like Adrian said. They are run on carpet mainly in Mod or when the traction is lower, but it’s really a driver taste type choice. The Parma Speed 8 feels faster in the corners IMO then the PF Speed 12. I like running with the PF Speed 12 when I run more then stock on carpet as it locks the car down more. I like them both and race with them both...they are for the most part the main bodies that are raced on about 90% of the cars on carpet. Just get both and try them out and see which you like better they are cheap enough.