These are replacement thumbscrews made of iron. They are to be used on the FPV and TILT models and that use aluminium thumbscrews for folks who prefer the extra strength that come with iron as opposed to aluminium which is lighter but a lot weaker. Note that these are not necessary on the GoPro front plate. The alumi thumbscrews are plenty strong for that. These iron thumbscrews are intended to be used on the folding arms mechanism. The aluminim thumbscrews may shear in a hard crash but these iron ones will not.