Made of high-quality carbide material, offering excellent wear resistance and durability. Precision-engineered with heat treatment and fine grinding for high accuracy and consistent performance. Designed for use with engraving machines and compatible with various bit tools and chucks. Provides strong clamping force and reliable grip stability. Specifications: Material: Carbide - 6.35mm to 12.7mm: Inner Diameter: 6.35mm (0.25 inch), Outer Diameter: 12.7mm (0.49 inch) - 6mm to 12.7mm: Inner Diameter: 6mm (0.23 inch), Outer Diameter: 12.7mm (0.49 inch) - 8mm to 12.7mm: Inner Diameter: 8mm (0.31 inch), Outer Diameter: 12.7mm (0.49 inch) - 10mm to 12.7mm: Inner Diameter: 10mm (0.39 inch), Outer Diameter: 12.7mm (0.49 inch) - 10mm to 12mm: Inner Diameter: 10mm (0.39 inch), Outer Diameter: 12mm (0.47 inch) - 8mm to 12mm: Inner Diameter: 8mm (0.31 inch), Outer Diameter: 12mm (0.47 inch) - 6.35mm to 12mm: Inner Diameter: 6.35mm (0.25 inch), Outer Diameter: 12mm (0.47 inch) - 6mm to 12mm: Inner Diameter: 6mm (0.23 inch), Outer Diameter: 12mm (0.47 inch) - 6.35mm to 9.5mm: Inner Diameter: 6.35mm (0.25 inch), Outer Diameter: 9.5mm (0.37 inch) - 6.35mm to 8mm: Inner Diameter: 6.35mm (0.25 inch), Outer Diameter: 8mm (0.31 inch) Package Includes: 1 Piece Router Bit Chuck Adaptor (Pack of 4)