This brake disc mounts to the wheel hub and provides the friction surface that pads clamp against to slow the vehicle. It measures 12.001 x 12.001 x 12.001 inches and is a replacement, sold individually.FeaturesPart number: CCD-9767Dimensions: 12.001 x 12.001 x 12.001 in.Unit of measure: EachTech SpecsHeight: 12.001 in.Width: 12.001 in.Length: 12.001 in.Unit of Measure: Each