Used for stitching metal or attaching to metal. A pre-drilled hole is required. Manufactured from A2 Stainless Steel for use where ultimate corrosion resistance. Stainless steel must be used where there is corrosive environment and/or the base material has inherent corrosive characteristics. Countersunk head gives a discreet finish into pre-countersunk holes Stainless Steel suitable for outdoor applications 60 self-tapping thread for ease of insertion" Gauge: 7 Length inch: 1 1/2 Thread Dia. mm: 3.9 Length mm: 38 Head Type: Countersunk Recess Type: Pozi Point Type: AB Point Driver Bit Size: PZ2 Material: Austenitic Stainless Steel (A2-304)Size 3.9 x 38 - 200 Pieces Timco Metal Tapping Screws - PZ - Countersunk - Self-Tapping - A2 Stainless in Silver