Stanley Proto J86000 Proto 5-Piece Super-Duty Chisels Set Made from S2 steel and specially heat-treated for greater strength and durability 20% larger striking surface than standard chisels directs the power to the cutting edge Longer shank features a knurl for better grip and easy positioning Hand ground cutting edge to the exact angle for cutting through tough metals Black oxide finish to help prevent rust corrosion; extending tool life and performance