Wooden Handle: The rod is made of solid wood, excellent grip and smooth operation. Durable: It is made of carbon steel and firmly coated with diamond-like grits. This ensures the long life of this file. High Efficiency: A flat file, works on fret edge and round fret end. You will appreciate the incredible efficiency of diamond. Diamond Abrasive: Medium coarse diamond abrasive for this application, use fret erasers to make the frets as smooth as butter. Four slots : Four slot gauges are provided in 1mm, 2mm, 3mm, 4mm. The 1mm slot works for extra narrow frets, like ukuleles. The 2mm slot works for all standard guitars, basses, mandolins, cigar box guitars. 3mm and 4mm slot works for jumbo frets. This means it will work on most stringed instruments.