These Forgefix Pozidriv Self-Tapping Screws are made from A2 stainless steel which will not corrode rust or stain with ordinary water like other steel does Their Pan Head with a flat under head surface makes the screw ideal to lay flat on sheet material of all types thus reducing deformation The screws tap their own thread in a pre-drilled pilot hole in sheet metal The screws are single threaded to resist pull-out APPLICATION Ideal for use in many DIY ironmongery engineering electrical and plumbing applications