Grip Rite P312STGDBK Star T-25 Bugle Head Coarse Thread Exterior Screw, 3-1/2" Feature a proprietary polymer coating that protects the fastener against corrosive elements Lifetime guarantee against rust and corrosion, including when used with treated lumber Stainless steel fasteners are recommended for all exterior applications For exterior applications, including decks, siding, gazebos, and play sets