Product Description Specifiaction: Gauge:16*124mm Power source: USB charging Work Rate:25W Transfer Speed:5000-25000r/min. Rated voltage:3.7v Diameter of bits:2.35mm around 30 minutes idling after full charge Sharp Tungsten Steel Bit The hardness of tungsten steel bit is 91HRA ,which often work on hard metal and glass,specially, it can help your glass etching work. Feature USB Power Charging: These electric jewelry drill powered by USB interface, it can meet your outdoor using after finishing charging.It can also be used while charging, but we suggest you to use after charging to extent battery using life. Power-off Protection: When etching tool encounter great resistance, it will shut off automatically to protect itself to extend using life.Then you just need to press ON/OFF button to start working again. 3 Speeds Selection These electric engraving pen can adjust speed from 5000 to 25000 r/min,The highest speed are also working on metal surface.Low noise design allow engraver pen keep quiet while working at high speed.