Precautions: 1. Please keep the file set clean and avoid water, oil or other contamination. 2. Please do not stack metal files with other tools. 3. Do not use a new file to grind hard metals with a hardness above HRC55. 4. Please do not use too much force when using the needle file to avoid breaking it. 5. To remove dirt from the file grooves, please use a cleaning brush. 6. Please choose the appropriate file size and use the file correctly.