They are the best pads I've ever used. Very grabby, rotor friendly and do not throw dust. I've also open tracked the car a couple of times. They are made for street and track/autocross.
From Porterfield
http://www.porterfield-brakes.com/pads.html
R4-S High Performance Street and Autocross
For high performance and heavy-duty street conditions. Perfect for prolonged everyday street use while also being capable of tolerating the most severe street use without any fade. Rotor friendly of course. The R4-S friction level will give you an impressive increase in stopping ability with very minimum pedal effort. R4-S compound has the absolute lowest noise and dust levels, far below OEM equipment or any other high performance brake material. Good for autocrossing, some drivers' schools, and rallies. The R4-S compound is available for virtually any vehicle sold in the US. We also offer the R4-S in pad sizes for competition type calipers that are used under street driven conditions.
Roscoe