These Forgefix Multi-Purpose Pozi Compatible Screws with countersunk heads are made from A2 stainless steel. They are ideal for use in and with many materials. APPLICATION Ideal for use in sanitary locations and in marine environments. Stainless Steel does not corrode, rust or stain with water as ordinary steel does, but despite the name it is not fully stain-proof, most notably under low oxygen, high salinity, or poor circulation environments. Stainless steel is used where both the properties of steel and resistance to corrosion are required. The Pozidriv screw is similar in appearance to the classic Phillips cross-head, but in fact is very different. The Pozidriv has four additional points of contact, and does not have the rounded corners that the Phillips screw drive has. The biggest advantage it offers is that, when used with the correct tooling in good condition, it does not cam out, allowing great torque to be applied. The Pozidriv screw can easily be distinguished by a line embossed in the screw head at 45 to the slots for the driver. The screws' countersunk heads are designed to sink flush with substrates to leave a smooth surface finish. They have single threads, designed to offer higher pull out values and quicker insertion. Multi-Purpose Pozi Screw Countersunk ST Stainless Steel 3.5 x 30mm Box 200