The PQ-M644-00 is the perfect option to replace and upgrade the nut on your Martin style acoustic guitar. ?It has an angled bottom and comes pre-slotted to make for a quick and easy install. TUSQ delivers a rich tone, crystal clear bell like high end with big open lows and a significant increase in harmonic content and harmonic sustain. Increase harmonics equals more richness and character in your tone. Its the difference between a four piece choir and a twelve piece choir singing Please note that all Graph Tech nuts are slightly long and wide to ensure extra room to achieve a perfect fit for your guitar. This extra material can easily removed with fine grit sandpaper.