MusicNomad Premium Truss Rod Wrench - 4mm for MARTIN® Guitar Models DSS, OMSS, Modern Deluxe Series, SC-13E and other Acoustic Guitar Brands (MN237)

Works on my Martin D-18 modern Deluxe (you need a 4mm for the MD as opposed to the 5mm for all their other guitars)

The usual MusicNomad of being well made with clean, precise tools - but pricey. The shape is a huge improvement on fighting with a 'standard' L-shaped allen keys as well, with the ball at the end particularly useful for lining the thing up properly. The handle is plastic but as solid as the rest.

This MusicNomad 4mm truss rod wrench is exactly what you want for your guitars. I use it on my Seagull and Epiphone acoustics. The fit is precise, with zero play, which gives real confidence when making small, careful truss rod adjustments. No slipping, no rounding. One thing I really appreciate is its versatility. It works equally well whether the truss rod adjustment is inside the sound hole or at the top of the headstock, which makes it extremely practical across different acoustic brands that use a 4mm truss rod. The build quality is excellent. It feels sturdy in the hand, the length provides good leverage without overdoing it, and the finish is clean and professional. If you do your own setups or want a safe, reliable wrench for seasonal adjustments, this is absolutely worth having in your case. Highly recommended.

The most common of the hex-style truss rod seatings are 4mm and 5mm. These are nice tools and are much more easier to use than the typical short-handled allen wrench that ships with most new guitars. MusicNomad seems to be attempting to simplify the DIY setup process with many of their new tools. Their efforts are much appreciated. I purchased both the 4mm and the 5mm.

Works and fits perfectly for my particular model of Martin. NOTE: CHECK YOUR MODEL, MARTINS USUALLY NEED A 5MM ALIEN KEY, THIS ONE IS 4MM. Don't mess around with a normal Allen wrench, this tool has one job and it does it correctly.