These are the little metal bits that hold your strings down behind the nut, on non-angled headstock guitars, so that they enter the tuning pegs correctly.
3 different colours, come with installation screws.
See our printable PDF to check for size - https://drive.google.com/open?id=19SBjQG8qR-agzPlFj9B-rJVhH5ghrQNB