Universal 1PC Multifunction 03-34mm Electronic Drill Bit Collet Mini Chuck Tool Set Fixture Clamp Micro Electric Drill Chuck Specification: Product name: Multi-functional electric grinding copper drill chuck + small wrench set. Material: Aluminum Ally + Brass. Clamping range: 0.3-3.4mm. Specifications (tail aperture): 2.0mm/2.35mm/3.0mm/3.17mm/5.0mm. Common DC motor selection specifications: 180 motor -- 2.0mm shaft diameter. 385 motor--2.35mm shaft diameter. 555 motor--3.17mm shaft diameter. 775 motor--5.0mm shaft diameter. Packing:1PC NOTE: For a motor whose model is unknown, or a motor whose shaft diameter is known but whose shaft diameter cannot be found, it is necessary to use a caliper accurate to 0.1mm to measure the precise motor shaft diameter, and then select the specification of the corresponding shaft diameter. _x000D_ _x000D_