Diamond fret files are the best way to recrown your frets! Unlike traditional fret files, diamond files cut in both directions, they don't chatter or leave chatter marks, and the fret is smoother after crowning. Because the diamond particles cut on the forward and backward strokes, you get better control over your work and the job goes much faster.
What grit do I need? If you're just starting out in fretting, we recommend the 300-grit files, as they don't remove too much material too soon — a mistake that many beginning fretters make. Even a professional will find the 300-grit file allows them to quickly get the fret properly crowned after only a few strokes.
Use the 150-grit when you need to mill-off lots of material in a hurry.