These rotors are approved by SCCA for club racings. Rotors are made of alloyed compacted graphite iron (CGI) and heat treated with tight machining tolerance in run out, parallelism, and thickness variation and have fine cross cut grinding disc surface. These rotors are extraordinary durable and can deliver much higher torque under extreme heat, we guaranteed them to outperform any competition's one-piece rotors. If you need that extra confidence to win the races these rotors are a must have.