Feature: *Hole Diameter: 6mm/ 6.35mm/ 8mm, 3 sizes meets different using needs. *Made of carbon steel, good flexibility and wear resistance. *Fine workmanship and stable performance, portable and easy to use. *High precision, tight and stable clamping, improve work efficiency. *Suitable for engraving machine, wood router, trimming engraving machine etc. Specification: *Material: Carbon Steel *Color: black+silver *Model: 6mm, 6.35mm, 8mm *Nut inner diameter: 7mm/8mm *Weight: about 50g *Quantity: 8pcs Package Includes: 3 x Router Bit Collet Chuck Adapter 3 x CNC Router Collet Chuck Adapter 2 x Clamping Nuts Note: 1. The real color of the item may be slightly different from the pictures shown on website caused by many factors such as brightness of your monitor and light brightness. 2. Please allow slight manual measurement deviation for the data.