Stainless Steel Torx Drive Flat Head Double Lock Screw for exterior use - these 1 5/8" long fasteners are the best I've ever used for 5/4 decking. Double ThreadLok™ design pulls and holds boards tight, preventing screws from backing out as lumber dries out. Ribbing on the seat of the screw head allows countersinks the screw without mushrooming. Torx plus drive means better grip with power drivers and less stripped screws. Suitable for marine and industrial applications where corrosion resistance is important.

While stainless steel offers the ultimate surface protection, it does not have the shear strength of a the comparable carbon steel HCR-X series. I would not recommend stainless steel for structural applications. They are great for decks, rails and sheathing.....especially exposed fasteners as the aesthetics are better.

These screws are sold in MasterPacks (five 1 lbs boxes per pack) and are drop-shipped directly from Spax. Spax has a $200 minimum to avoid small order surcharges.

Comparison Photo - standard vs doublelock stainless screw