This is a set of three replacement medium grit stones and cotter pins for Powerbuilt product #648439 or another cylinder hone deglazer.These high-quality 4″ medium grit stones (#220) are designed to deglaze engines on a cylinder hone. Set also includes corresponding cotter pins Any automotive specialty tool makes an automotive repair or maintenance task easier, but Powerbuilt takes the concept of help a big step further. Every package comes with professionally written usage instructions and photos that take you step by step through proper tool usage.Dependable Powerbuilt specialty tools offer power and style.