For attaching friction stays with countersunk holes to steel reinforced PVCu frames. Thread Dia. mm: 3.9 Length mm: 25 Head Type: Shallow Pan Countersunk Recess Type: Phillips Thread Type: Self-Tapping Point Type: Self-Drilling Finish: Zinc Material: Carbon SteelSize 3.9 x 25 - 1000Pcs Timco Window Screws -Friction Stay -Shallow Pan Countersunk -PH in Silver