graphtech tusq xl man-made guitar nuts graphtech tusq xl nut - fender precision 4 string nut designed to boost guitar performance, tusq xl is precision engineered and specially formulated to bring out the hidden harmonics and richness in every note. tusq xl is based on the highly resonant tusq man made ivory and impregnated with ptfe, the slipperiest substance on earth, to improve the tuning performance of the guitar. improved tuning stability, improved harmonic content