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The "S" is for street. These are a long-time favorite of ours for performance street driving. They work great for street/autocross and very light track duty. They dust a bit but not as much as the Hawk HP Plus and the performance is consistent from street temps to about 500. For more serious duty try the Porterfield R4-1 and R4.
Carbon Kevlar construction. One set needed for front. Does not include replacement springs, clips, etc.