The hardest but most brittle of the solid bits, always use a drill clamp or guide.

Tungsten Carbide Steel Double Cut Rotary Burrs Set for Rotary Tool, 10pcs 1/8 inches Shank Fits Rotary Tool for Grinder Drill, DIY WoodWorking Carving, Metal...
4.0

Hakkin 10PCS Double Cut Carbide Burr Set 1/8” Shank Drill Bits Tungsten Carbide Rotary Burr Set for Woodworking, Drilling, Metal Carving, Engraving,...
5.0

Carbide Burr 1/4" Shank, SL-4 Tungsten Double Cut Rotary Die Grinder Bits - Cutting Burrs for Milwaukee, Dewalt and Makita Die Grinder Accessories - Wood...
4.0