These long lasting, industrial grade grinding wheels are designed for use with the Drill Doctor model DDSB Spade Bit Sharpener. Includes one coarse wheel (white - 46 grit) and one fine wheel (red - 60 grit). The coarse wheel is intended for use when sharpening severely damaged or dull spade bits. The fine wheel is intended for use when touching up or re-sharpening spade bits.