product USB power charging These electric jewellery diamonds are powered by a USB interface, which can satisfy you for outdoor use after charging. It can also be used while charging, but we recommend that you use it after charging to extend the life of the battery. Power failure protection When the etching tool encounters greater resistance, it will automatically shut down to protect itself and prolong its service life. Then you just need to press the on/off button to start working again. 3 speed options The speed of these electric engraving pens can be adjusted between 5000 and 25000 r/min. The lowest speed allows you to polish your nails safely, and the highest speed can also work on metal surfaces. These engraving machines are suitable for hobbyists and professionals, allowing you to create unique marks on wood, steel, metal, glass, ceramics, diamonds, leather, plastic, bamboo, and statues. Anyone can complete personalized items, such as unique stones, jewelry, pet tags, keychains, and beautiful marked cups.