StewMacFretbar Understring Leveler, 9" Length – Perfect for Ukulele & Mandolin – Spot & Full-Scale Guitar Fret Leveling – Professional Luthier Tool – Works with Strings On or Off

This is a lifetime tool. It is solid and heavy, and works exactly as it is was meant to. It came with string spacers and it also has a tubular case. Great design and a great tool.

Works great without the need to remove strings and StewMac items are outstanding and worth the money because there's no need to risk buying junk since all of their products are top quality based on my subjective experience using them. You can find items that are cheaper, but they are not equivalent in quality IMO.

It is a large tool. Using with and without under string feature. Very heavy enabling a relaxed stroke for fret leveling.

TL;DR - Great tool if you find you're getting mediocre results leveling frets with simulated string tension and are willing to invest more time & effort to get better results. Otherwise, get a FretGuru beam - they're dead flat and easier to use.I'm an engineer, so keep in mind that's my perspective here. The bottom on the StewMac bar/beam I received is very flat - no daylight when checking against an 18" Starrett 385. This bar is more hefty than you would think for aluminum which makes it more rigid (and more likely to stay flat) than something with a similar profile and thinner cross-sections. But, the additional weight and 5/64" thick base can also make it a little harder to use for under-string leveling. Rhynostick RedLine PSA rolls work well with it, but Dura-Gold Premium rolls may work just as well for less.I've found using this beam/bar to level frets with strings on the guitar and tuned to pitch gets me better results than other methods attempting to simulate string tension. HOWEVER, it's definitely more time consuming with more steps to get those results. First, you have to raise the strings high enough to clear the 5/64" base of the bar. Not usually a problem at higher frets, but the closer you get to the nut the more the base of the bar gets pinched between the strings and the frets. You have to lift the strings at the nut either with some type of insert between the strings and fretboard (a spacer is included) or with a Nut Height Extender (a real thing) over the nut to keep the strings from interfering. I found the included spacer was too short and had to add shims underneath it. Second, your range of motion for sanding is limited to the space between the strings. You can avoid faceting the fret tops by sanding in a X pattern across them following the contour/radius of the fretboard instead of just sanding in one direction parallel to the strings. BUT, it takes a lot of time and attention to detail to do that consistently and evenly across all five gaps. Both of those things - raising the strings and sanding between them - are a pain, and the effort involved likely passes the point of diminishing returns if you level frets on a regular basis. Still, if you're looking for more precise results...(see "engineer" above).This bar/beam can be used to level frets with strings on or off, so if you only want to invest in one tool that can do both this would be it. Otherwise, I prefer the profile, weight and precision of the FretGuru leveling beams.

Essential Stew Mac tool.

I use 11-54 in E std, on a Jackson with a thin neck. Being able to make any adjustment under tension is a great thing, and after only a few hours this evening messing around to get a feel for it (on some old beaters) and then hitting a few high spots that have bugged me for years on my Jackson, I am very impressed and eager to see how much I can accomplish. It's already far and away the best money I ever spent on fret tools, hands down.

Bought for my brother for Christmas and he is completely happy.

I use this one more than the longer one because I feel like it gives me a bit more control. Using this under the strings while the guitar is up to full tension saves me tons of time leveling frets. Have tried other systems but none compare to this.