Fermacell 3.9 x 30mm Collated Screws Compatible with most brands of screw guns and protected against corrosion with a self counter sinking head. For fixing fermacell boards to timber or fermacell steel subframes /50 pcs per strip. It is recommended to use 13 screws per m² for walls (for each side) and 30 screws per m² for ceilings. (box of 1000)