The PT-6134-00 is a great option to replace or upgrade the nut on your six string acoustic or electric guitar. It has a flat bottom and is pre-slotted for a quick and simple install. Black TUSQ XL is engineered from the same material as TUSQ and is impregnated with PTFE which is five times more slippery than graphite. It has all the tonal benefits of TUSQ, bringing out the hidden harmonics of your guitar all while drastically improving tuning performance. Note: All Graph Tech nuts and saddles are slightly long and wide to ensure extra room to achieve a perfect fit for your guitar. This extra material can easily be removed with fine grit sandpaper.