The Graph Tech PQ-M175-00 is a pre-slotted, flat-bottom replacement nut for Martin-style acoustic guitars and others with a 1.75-inch nut width. It is made from TUSQ, a man-made material offered as a consistent-density alternative to bone and ivory. The pre-cut slots and string spacing simplify installation. Graph Tech states TUSQ efficiently couples string vibration to the guitar for added harmonic resonance and sustain.