Good to know. I was mainly thinking about the yellows for track days. I don't auto x, just strip. Thought it would be beneficial if I could stiffen the rear shocks up for those days. I have stock shocks with progress springs right now.CSS Turbo rear shocks are a helluva lot cheaper and work very very well with all of the after market springs currently available for the IRL, notably the Pedders and Progress. Not adjustable, but they're pretty dead on for lowering springs as is. I have the Yellows and I love them, but in retrospect I would have bought CSS/T front struts and MAYBE Koni Yellows for the rear for Stock class autocross just 'cuz they can go stiffer. If you're not heavy into the Solo where heavily overdamping the rear is the way to go, the CSS/T are awesome for the rear as well.