Adopt carbide material, good flexibility and wear resistance. High precision, tight and stable clamping. Made of carbide, processing 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/ 0.25inch outside diameter:12.7mm/ 0.49 inch 6mm to 12.7mm: Inner diameter: 6mm/ 0.23inch outside diameter:12.7mm/ 0.49 inch 8mm to 12.7mm: Inner diameter: 8mm/ 0.31inch outside diameter:12.7mm/ 0.49 inch 10mmto 12.7mm: Inner diameter: 10mm/ 0.39inch outside diameter:12.7mm/ 0.49 inch 10mm to 12mm: Inner diameter: 10mm/ 0.39inch outside diameter:12mm/ 0.47 inch 8mm to 12mm: Inner diameter: 8mm/ 0.31inch outside diameter:12mm/ 0.47 inch 6.35mm to 12mm: Inner diameter: 6.35mm/ 0.25inch outside diameter:12mm/ 0.47 inch 6mm to 12mm: Inner diameter: 6mm/ 0.23inch outside diameter:12mm/ 0.47 inch 6.35mm to 9.5mm Inner diameter: 6.35mm/ 0.25inch outside diameter:9.5mm/ 0.37 inch 6.35mm to 8mm Inner diameter: 6.35mm/ 0.25inch outside diameter:8mm/ 0.31 inch 6.35mm to 8mm Inner diameter: 6.35mm/ 0.23inch outside diameter:8mm/ 0.31 inch Package Includes:(4 Pack) 1Pieces Route Bit chuck adaptor