ForgeFix TechFast Timber to Steel CSK/Wing Screws are designed for joining timber to steel frame buildings. These screws feature breakaway wings that create a clearance hole, preventing the thread from engaging with timber during drilling. The wings ream a hole and then break off upon contact with the metal surface, allowing the thread to engage with the metal. They are equipped with a TORX compatible insert for enhanced power transmission and have recessed ribs for improved countersinking. These screws offer fire and corrosion resistance and comply with EU Safety, Health, and Environmental requirements. Specifics: Size: 5.5 x 120mm, Clamping Thickness: 91mm, Effective Thread Length: 92mm, Pack Size: 50, Drill Tip: No.5. The No.5 drill tip is suitable for self-drilling heavy gauge steel up to 12.5mm.