Designed to boost guitar performance, the PT-6011-00 Black TUSQ XL boasts precision engineering and is specially formulated to bring out the hidden harmonics and richness in every note. It’s based on the highly resonant TUSQ manmade ivory and impregnated with PTFE, the slipperiest substance on earth, to improve the tuning performance of the guitar. When in doubt, use this one, you can always sand the bottom of the nut to adjust lower.