EBC X-Series Brake Disc MD633X. Hand built by trained engineers, these are no production line mass produced product. British made discs using German mill rolled precision stainless steel rotor blades mounted onto lightweight alloy centre hubs, using the EBC patented SD square drive button technology. Square drive buttons resist loosening and prevent vibration common with low cost circular rivets or buttons. Rotor blades are diamond cross ground for ultra smooth flat finish for fast and perfect brake pad bed in. All EBC discs are 100% inspected for accuracy and runout. 1x MD633X EBC Brake Disc. Product Type: Brake Discs. Inside Bore Diameter: 63mm. Number of Holes: 6. Distance between Hole to Hole: 40mm. Pitch Circle Diameter (PCD): TBA. You can send us a message by using the “Questions and answers” section towards the bottom of the page.