BFGoodrich says they are the same tire compound as the KD series. Also, read this on epinions.com from a reviewer:
"It is a little advertised fact that these are the same street tires used in the Skip Barber Race Series on the R/T 2000 open wheeled formula cars for their Regional, National and Masters race series at race tracks all over the country.
Having driven 10 race weekends and approx. 20 lapping sessions on these tires at tracks including Sebring, VIR, Mont-TrembIant and Lime Rock Park I can confirm that their on-track performance is outstanding. On a 1200 lb. open wheeled race car they have excellent grip in both wet and dry conditions, are very predictable and offer as much grip and comparable lap times to the racing slicks that were abandoned after these tires came along. Having driven them at over 100mph in heavy rain on three different occasions I can also attest to their superior wet weather performance in extreme conditions."