Features: Made of high-quality carbon steel, sturdy and durable for long life. 8 various types to meet your different needs. Start slowly, wait for the balance to improve, then gradually accelerate. High precision woodworking milling cutter chuck can be perfectly combined with your engraving machine to clamp the tool securely and improve work efficiency. Please ensure that the router collet extension is properly assembled. Note that the extension shank should be secured tightly, and the collet nut should be tightened with the same pressure as any standard router collet. Specifications: Material: Carbon Steel. Type: 8 types (optional). 6mm shank to 6mm shank (A). 1/4" shank to 1/4" shank (B). 1/4" shank to 8mm shank (C). 8mm shank to 12mm shank (D). 8mm shank to 1/2" shank (E). 8mm shank to 8mm shank (F). 12mm shank to 12mm shank (G). 1/2" shank to 1/2" shank (H). Package Size: 100x30x30mm / 3.94x1.18x1.18in. Package Weight: 110g / 3.88oz (A, B, C); 135g / 4.76oz (D, E, F); 145g / 5.11oz (G, H). Packing List: 1 x Router Bit Collet Extension