Used when constructing drywall track and ceiling track systems to stitch the track together (Max. 3.0mm) without the need to pre-drill a hole. Fire Classification: A1" Thread Dia. mm: 4.2 Length mm: 19 Head Type: Wafer Recess Type: Phillips Point Type: Self-Drilling Driver Bit Size: PH2 Finish: Zinc Material: Carbon Steel Max Drilling Thickness mm: 3.0Size 4.2 x 19 - 1000 Pieces Timco Metal Construction Sheet & Framing Screws - PH - Wafer - Self-Drilling in Silver