Forgefix drywall screws have a zinc plated finish for increased durability. The screws come complete with a Phillips number 2 insert bit. Their bugle head allows the screw to sink effortlessly into the dry lining without the need for countersinking which in turn minimises the damage to the surface. Designed for fitting dry linings to studding. Zinc coatings prevent oxidation of the protected metal to create a longer lasting finish. It does this by forming a barrier and by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not trigger a breakdown of the substrate surface integrity as it is formed. The zinc oxide, if left intact, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminium and stainless steels by their oxide layers. The Phillips screw has four simple tapered slots. It is designed so that a Phillips tip screwdriver can turn a Phillips screw with increasing torque. When the torque gets to be too strong for the tip then the screwdriver tip winds itself out of the screw thus preventing over tightening and or damage to the screw head. Fine thread screws have an extremely sharp point which not only pierces the plasterboard skin but will also allow the screw to drill through thin steel base structures. Supplied in box. Size: 3.5 x 25 mm.