GRK RSS Rugged Structural Screw has a patented design and made of specially hardened steel to provide customers with high tensile, torque and shear strength. The sharp threads and points bite instantly into material, including hardwood, reducing the splitting effect due to smaller shanks. The GRK RSS series screws that are 3-1/8 in. and longer have 6 CEE threads which enlarge the screw hole for the non-threaded portion of the fastener, allowing the wood to settle easily and increases the screw's drawing strength.. Drive Style: Torx. Fastener Color: Brass. Fastener Material: Carbon Steel. Fastener Plating: Electro Galvanized Zinc. Fastener Type: Structural Screws. Features: ACQ Rated,Self Tapping. Grade: Not Graded. Head Style: Low Profile Head. Included: Driver Bit. Interior/Exterior: Exterior,Interior. Measurement Standard: SAE. Measurement System: Inches. Package Quantity: 45. Product Weight (lb.): 0.036 lb. Returnable: 90-Day. Thread Pitch (mm): 3.5 mm. Thread Style: W-Cut Thread. Threads Per Inch (TPI): 8 TPI. Screw Length: 3-1/8 in. Size: 5/16 in. Screw Length: 3-1/8 in. Head Style: Low Profile Head. Package Quantity: 45. Size: 5/16 in. Drive Style: Torx. Fastener Material: Carbon Steel. Interior/Exterior: Exterior. Fastener Type: Structural Screws