Four gauges slot for different fret sizes: This fret crowning file set includes four gauges slots in 1mm, 2mm, 3mm, and 4mm. The 1mm slot is suitable for extra narrow frets like ukuleles, the 2mm slot works for standard guitars, bass, banjo, mandolin, and box guitars, and the 3mm and 4mm slots are perfect for jumbo frets.
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