Cylinder Block Material: Aluminum Alloy ADC6, process by CNC machine Cylinder Liner Material: Boron alloy cast iron, the inside wall adopts German fillet grinds Block Surface Roughness: 1.6- 3.2 Ra Block Hardness: HBS70-85 Liner Inside Wall Roundness: ≤0.008mm Liner Inside Wall Roughness: ≤Ra 0.4 Liner Inside Wall Hardness: HRB93-104