Best Focus Range: 30-50mm Best Focus Length: 100mm Safety Warning: There has warning signs, If the machine has moved or overturns, the laser will be turned off automatically. The product is a laser carving machine for home use, a tool machine, can not be compared with laser carving machine for industrial use. Do not use the laser head to point at human or livestock, do not use laser to point at people's eyes.Skin exposure to laser is strictly prohibited. The caving machine should not be stopped while working, it will cause a damage. This product not suitable for kids under age of 14. Software can support Operating System: WIN-7/8/10; IOS, Android. Do not fall or make any collision to the product. Metal, glass, crystal and transparent or translucent stuff are can not be engraved. The color of the item may vary slightly due to photography and different PC monitor, and the size might be slightly errored due to manual measurement. Your kindly understanding would be appreciated. You might need to temporarily shut down the antiviruss software before downloading the software. Otherwise some files in the software would be mistaken for viruss and deleted by antiviruss software. Please according to the user manual to operate the machine. After 20 minutes of working, it need to take a break, can not work continuously for a long time.