This is the smallest round carbide cutter available. This burr is .3mm in diameter, which is 40% smaller than our next smallest burr at .5mm in diameter (1/4 Carbide). This is a great tool for engraving intricate details under magnification. Pictured is the 1/4 Carbide because the 1/8 is too small to get a clear view without magnification. These round burs are rated by size. Carbide rounds are excellent for cutting through stenciled are most popular for wood and metal, with some application on glass and stone.