Replacement bit for Runwell STEX & STEX90 tools. Available in 3mm/4mm and 5mm/6mm sizes. ⓘ If the bit becomes loose, use a 2.5mm allen wrench and tighten the set screw on the end of the tool that secures the bit. Adding a tiny drop of blue threadlocker will prevent the set screws from needing adjustment. Specifications • made in Japan • material: steel