Features:Made of high-quality carbon steel, sturdy and durabl-e for long life.3 various types to meet your different needs.Start slowly, wait for the balance to improve, you can slowly accelerate.High precisio-n woodworking milling cutter chuck can be perfectly combined with your engraving machine to clamp the engraving machine stably and improve work efficiency.Please ensure that the router collet extension be properly assenbled. Please make a note that extension shank should be secured tightly; while collet nut should be tightened only with the same pressure as any router collet.Specifications:Material: Carbon SteelType: 3 types(optional) 1/4" shank (A) 1/2" shank(B) 8mm shank (C)Package Size: 120*70*20mm/4.72*2.76*0.79inPackage Weight: 110g/3.88oz(A) 85g/3oz(B) 135g/4.76oz(C)PackingList;1*Router Bit Adaptor