ITEM NAME:6.35mm to 3.175mm 1/8" Engraving Bit CNC Router Tool Adapter for 6mm Collet 3c Material : Spring steel Function : Engraving bit CNC router tool Adapter 6.35mm to 3.175mm 1/8" Size  Dia. (Outer): 6.35mm ,Dia. (Inner): 3.175mm(+/-0.1mm) Length: 6mm Package Included: 1 pcs CNC router tool Adapter.Length: 6mm.