Features: 1. Made of high quality carbon steel, sturdy and durable for long life. 2. 3 different types to meet your different needs. 3. Start slowly, wait for the balance to improve, you can speed up slowly. 4. The high-precision woodworking router chuck can be perfectly combined with your engraving machine to clamp the engraving machine stably and improve work efficiency. 5. Please ensure that the router collet extension piece is properly mounted. Please note that the extension shaft should be clamped firmly, while the collet nut should only be tightened with the same pressure as any router collet. Specifications: Material: Carbon steelType: 3 types (optional) Shank 1/4 (A) 1/2 Rod (B) 8mm Rod (C) Package Size: 120*70*20mm/4.72*2.76*0.79inPackage Weight: 110g/3.88oz(A) 85g/3oz(B) 135g/4.76oz(C) Packing List; 1*Router Bit Adapter