High-quality materials: The engraving and cutting machine chuck is made of carbon steel materials, which has good flexibility and wear resistance. Hole diameter: 6mm/6.35mm/8mm, 3 sizes meet different using needs. Also comes with 2 nuts. Woodworking tools: The router collet is suitable for engraving milling wood, automobiles, molds and mechanical engineering. Is the perfect woodworking tool for engraving machine, wood router. Easy to carry: The milling cutter chuck is easy to carry, has very precise clamping, tight and stable, and improves work efficiency. Easy to use: Fine workmanship, stable performance, very easy to use. Features: Hole diameter: 6/6.35/8mm. Quantity: 6pcs (2pcs for each size) +2pcs nuts Material: carbon steel. Height: 3pcs 20mm, 2pcs 8.4mm, 1pc 7mm High strength and hardness. Easy to use. Durable in use. Package includes: 2pcs * 6mm Collet Adapter. 2pcs * 6.35mm Collet Adapter. 2pcs * 8mm Collet Adapter. 2pcs * Nuts 2-3cm difference exists due to different measuring way, please confirm the detailed size before ordering, thanks for your understanding & cooperation. According to the difference of screens and light, please allow slight color difference.