1. The revolutionary new tool fretbar understring leveler lets you level your frets under full tension without removing the strings. You can level your frets with the strings ON.  2. Material: High quality material -CNC machined with nice oxidation blasting treatment. High glossiness, durable and long-lasting use, not easy to deform.  3. Applicable for fret, saddle, and fingerboard sanding, great accessory for players and luthiers. Suitable for the fret leveling of electric guitar, acoustic guitar, electric bass, banjo, mandolin, etc.  4. Used with the strings on or off, the precision-ground surface works quickly and accurately to get frets level.  There is a Fretbar for every leveling job:  4.5inch length (114mm) perfect for spot leveling problematic frets all over the neck. It's also perfect for creating fallaway on acoustic guitars.  9inch length (228mm) is designed for smaller necks like ukuleles and mandolins. It also works for leveling full scale necks and spot leveling.  13.8inch length (350mm) is universal  18inch length (457mm) makes it easy to level an entire neck. You'll quickly and evenly level most of the frets at the same time, without the added danger of running into the nut, saddle, or hardware.  weight: 358g / 545g / 700g / 176g  Color:Black  Material:Aluminum alloy  Size:228 x 38mm / 350 x 38mm / 457 x 38mm / 114 x 38mm    Package Contents:  1 x Sanding beam    Only the above package content, other products are not included.  Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.