Silicon carbide grainClosed coat structure for more material removal on various materialsRecessed center hole helps avoid scratching of the surfaceAvailable in Bulk or Blue Line??????????Packaging, Resin over resin construction for a strong bond that is resistant to heat and moistureVulcanized fiber backing for heavy duty sandingAvailable in bulk and Blue Line??????????packagingCustom Discs: All custom fiber discs are non-cancellable and non-returnableBacking Pads for Fiber Discs?????re available in Accessories