Prevents overheating during extreme driving such as sports driving. Also used for motorsports. The open valve pressure is changed from a standard car 108 KPa (1.1 kg/cm2) to the open valve pressure of 127 KPa (1.3 kgf/cm2) to increase the boiling point of coolant. The seal is made of silicone rubber with excellent heat resistance, compression, permanent distortion, and oil resistance. [Compatibility] Lancer Evolution 4,5,6,7,8,9,10 (CN9A,CP9A,CT9A,CT9W,CZ4A).