The Cortex Hidden Fastening System is the fastest, easiest way to hide fasteners on Trex stairs, perimeter boards, and more. New wobble-free bit design and collated plugs. Making a strong connection a whole lot easier.. Drive Style: Torx. Fastener Color: Black. Fastener Material: Carbon Steel. Fastener Plating: Painted. Fastener Type: Composite Deck Screws. Features: No Additional Features. Grade: Not Graded. Head Style: Low Profile Head. Included: Driver Bit. Interior/Exterior: Exterior,Interior. Measurement Standard: ASTM. Measurement System: Inches. Package Quantity: 224. Product Weight (lb.): 4.80 lb. Returnable: 90-Day. Screw Head Color: BLACK. Thread Pitch (mm): 0.3 mm. Thread Style: Coarse Thread. Threads Per Inch (TPI): 12 TPI. Screw Length: Assorted. Size: #9. Screw Length: Assorted. Head Style: Low Profile Head. Fastener Material: Carbon Steel. Size: #9. Fastener Type: Composite Deck Screws. Thread Style: Coarse Thread. Drive Style: Torx