Designed for attaching dense board to timber stud work. The super sharp point and high low thread is specially designed for an excellent fixing into timber. Phillips No.2 recess for a positive drive Countersunk head for improved countersinking into the dense board High-Low thread for increased pull-out value into both timber and thin sheet metal Coarse thread for extreme hold Fire Classification: A1" Thread Dia. mm: 3.9 Length mm: 55 Thread Length mm: 50 Head Type: Reduced Countersunk Recess Type: Phillips Point Type: 25 Sharp Driver Bit Size: PH2 Finish: Black Phosphate Material: Carbon Steel Max Drilling Thickness mm: 0.6Size 3.9 x 55 - 1000 Pieces Timco Drywall Dense Board Screws - PH - Reduced Countersunk - High-Low in Black