Master Cylinder Support for 15-20 WRX/STI BlackPSP BRK 403 OVERVIEW The PERRIN Master Cylinder Brace prevents unwanted movement of the master cylinder, allowing for increased brake pedal stiffness and response. REDUCE FLEX Your brake pedal is connected to the thin sheet metal firewall which flexes as you apply the brakes. The firewall is not stiff enough to deal with the constant and repeated forces while applying the brakes. The PERRIN Master Cylinder Brace creates a bridge between the firewall,