Roller string retainer replaces the string retainers on most electric guitars. It provides a smooth path for the strings to the machine heads reducing friction and makes tuning easier and improves sustain.
It is fitted behind the nut and the strings run under the retainer then on to the machine head. Each retainer will retain 2 strings.
the spacing of the strings at the retainer is 7mm and the height of the string at the retainer is 8mm.
One supplied with screw.