PHEINOXâ„¢ 305 stainless steel screws are corrosion and stain-resistant fasteners designed to withstand wet environments. PHEINOXâ„¢ 316 stainless steel screws are designed for coastal applications. GRK's patented R4, RSS, FIN/TRIM and RT composite screws are available in PHEINOXâ„¢ stainless steel. GRK recommends PHEINOXâ„¢ 305 stainless steels screws for applications that require superior corrosion resistance in wet environments such as decks, boardwalks, pools and hot tubs. PHEINOXâ„¢ 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. PHEINOXâ„¢ 305 stainless steels screws are recommended for applications located more than 1 mile from the coast.