Diablo's steel flap discs feature a premium zirconium grit blend for up to 10 times faster material removal compared to standard grinding wheels. The special flap design of the discs offers flexibility and provides a cushioned grinding effect. Diablo's high performance flap discs combine two steps in one at the same time grinding and polishing. - See more at: http://www.diablotools.com/products/product/DCX045040N01F#sthash.04snZjIS.dpuf