features 13 round files and 1 flat file, with a grinding stone, universal for string instruments, such as guitar, mandolin, bass, ukelele and banjo etc. It will make the string slots very smooth. Features: Universal for string instruments, guitar, mandolin, bass, ukelele and banjo etc. 13 dimension(4mm-16mm) round files for polishing the string slots, and it makes the string slot very smooth. 1 flat file for burnishing the nut and bridge. Comes with a grinding stone. Made of high quality metal, compact and sturdy.