1、It is made of tungsten steel material and has higher hardness, higher strength, corrosion resistance and rust resistance than ordinary carving knives. 2、The unique mirror friction treatment is used to create a perfect surface effect and reduce the possibility of burning and deviation. 3、The perfect choice for carving and carving details, professional carving accessories. 4、It has a wide range of applications, mainly for engraving and marking on wood, MDF, aluminum, and acrylic. 5、Comes with 11pcs in total, different sizes, which is made to meet your different needs. 11 x Engraving Bit Item Type: Engraving BitsMaterial: Tungsten SteelColor: Plating BlueSpecification:4x 0.5x25, 4x 0.4x30, 4x 0.3x30, 4x 0.3x25, 4x 0.4x25, 4x 0.5x15, 4x 0.4x15, 4x 0.5x20, 4x 0.6x20, 4x 0.3x20, 4x 0.4x20Shank Diameter: Approx. 4mm/ 0.2inTotal Length: About. 45-50mm/ 1.8-2in  (left and right)Purpose: Embossing / lettering / hole openingApplication: For Spring carving tools, CNC milling machines, end mills, etc.