The Collated Cortex Hidden Fastening System for Decking is a 2 pack of 2-1/2 inch composite deck screws in stone gray color. These electro galvanized zinc fasteners are made of carbon steel with a coarse thread style and a low profile head design. The package includes a driver bit and has a total length of 12 inches, making them suitable for exterior use in deck building and hardware applications. With a brand like FastenMaster and a measurement standard of ASTM, these fasteners provide a secure and durable option for fastening decking materials.