Stainless Steel The steel used in the EBC rotor blades is a special stainless blend with higher friction effect than normal heat treated stainless steel found on stock discs. Boasts up to 10% improvement in friction effect improving brakes even further. Weight of the X and XC series is reduced by 5-10% by using a six only button drive system on a lightweight alloy centre hub, which once again grabs the lead over stock parts. The SD-System™ uses a square-sided rivet with many advantages. The SD-System™ of square-sided buttons means that the rotor can expand inwards and outwards unrestrained and that perfect rotor functionality is retained at any speed or load.