Voltage: 4.2V Speed: 5000-18000r / min Clamping Diameter: 2.35mm (Suitable for all 2.35MM specification grinding head, reducing drill etc) IMPROVED WIRELESS ELECTRIC GRINDER PEN: This grinding pen comes with rechargeable lithium battery, so you can use it anywhere. 3 speeds: 5,000 to 18000 RPM output makes the rotary tool more prominent. Three gear selection can apply to different situations precisely, and make your projects easier and more professional. Dual Usage: Charging and plugging in dual usage, can be connected to the power supply while charging, more efficient. Package Include: 1 * Engraving pen 1 * USB Power wire 2 * Drill bit 3 * Saw blades 30 * Bits 1 * Tungsten steel bit 1 * Connecting stick NOTE 1. It must be fully before the first use. 2. Not suitable for carving, punching, cutting, grinding. 3. Noise and temperature during machine operation are normal phenomena. Colour: Material:Metal Package Contents: 1 set x engraving machine Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.