For reshaping your abrasive stones. Made from coarse silicon carbide with 4 half round grooves: ¹⁄₁₆", ¹⁄₈", ³⁄₁₆", and ¹⁄₄". Overall dimensions: 3 ¹⁄₂" x 1 ³⁄₈" x ⁹⁄₁₆" high.