Deck Screw( Square Drive,Type-17,Nibs, Sharp Coarse Threads) Used in decks,heavy pollution area,For example:dock, Deck Screw( Square Drive,Type-17,Nibs, Sharp Coarse Threads)Used in decks,heavy pollution area,For example:dock,hot spring applications , fences and other Outdoor applications.Surface Treatment:Salt Spray Test:500-1200 hoursColour: Red,Green and so on Deck Screws