PHEINOX stainless steel screws are made from only the best grade of stainless steel wire, 305. The unique characteristics of the PHEINOX wire give our stainless steel screws unmatched performance, by maximizing both torque and increasing bending strength. GRK recommends PHEINOX 305 stainless steel screws for applications that require superior corrosion resistance in wet environments such as decks, boardwalks, pools and hot tubs. PHEINOXTM 305 stainless is also recommended for use with cedar, red-wood and various other wood substrates that have higher acid content as well as for composite deck boards. PHEINOXTM 305 stainless steel screws are recommended for applications located more than 1 mile from the coast.