Adopt high quality carbide material, good flexibility and wear resistance. High precision, tight and stable clamping. Made of carbide, processed by heat treatment and precise grinding. Suitable for engraving machine, applicable to different specifications of the bit tool and chuck. Good elasticity and abrasion resistance. High precise clamping force, good grip stability. Specification: Material: Carbide 6.35mm to 12.7mm: Inner diameter: 6.35mm / 0.25 inch Outside diameter: 12.7mm / 0.49 inch 6mm to 12.7mm: Inner diameter: 6mm / 0.23 inch Outside diameter: 12.7mm / 0.49 inch 8mm to 12.7mm: Inner diameter: 8mm / 0.31 inch Outside diameter: 12.7mm / 0.49 inch 10mm to 12.7mm: Inner diameter: 10mm / 0.39 inch Outside diameter: 12.7mm / 0.49 inch 10mm to 12mm: Inner diameter: 10mm / 0.39 inch Outside diameter: 12mm / 0.47 inch 8mm to 12mm: Inner diameter: 8mm / 0.31 inch Outside diameter: 12mm / 0.47 inch 6.35mm to 12mm: Inner diameter: 6.35mm / 0.25 inch Outside diameter: 12mm / 0.47 inch 6mm to 12mm: Inner diameter: 6mm / 0.23 inch Outside diameter: 12mm / 0.47 inch 6.35mm to 9.5mm: Inner diameter: 6.35mm / 0.25 inch Outside diameter: 9.5mm / 0.37 inch 6.35mm to 8mm: Inner diameter: 6.35mm / 0.25 inch Outside diameter: 8mm / 0.31 inch Package Includes: 1 Piece Router Bit Chuck Adaptor (2 Pack)