. * Four gauge socket is in 1mm,2mm,3mm,4mm. 1mm works for extremely narrow frets, likes ukulele; 2mm works for all standard guitars, bass guitar, banjo, mandolin, guitar cigar box; 3mm, 4mm socket works on jumbo sills. This means that it will work on most stringed instruments. * One flat file, works on the edge of the threshold and the round end of the threshold. You will experience the amazing performance of the diamond. * Compatible with--not only suitable for crowning guitar fret, but also for electric guitar, acoustic guitar, bass, Ukulele, etc.; A nice simple way to crown the frets if worn. * Diamond abrasive for coarse for this application, use threshold rubber bands makes the thresholds smooth as buttery. * It is made of high quality carbon steel and heavily coated with diamond grits. Which ensure the long life of this file. Specifications: Color: As shown in the picture Material: Carbon Steel + Diamond Grit + Wood Handle Product Size: 95 * 10 * 10mm / 7.7 * 0.4 * 0.4in Net Weight: 140g / 0.32lb Package Included: 1x Threshold is your file 2 x Threshold Protection Sheet