The Bossard M4/BN531 is a heavy-duty, adjustable-length, spring loaded, self-locking fastener that is designed for use in metal-to-metal applications. It is made of high-grade stainless steel, making it resistant to corrosion and rust. The M4/BN531 is most commonly used to secure panels, covers, and other components in the transportation, aerospace, and general industrial markets. It has a built-in lever and an adjustable nut which allows for quick assembly and re-assembly without the need for a tool. The M4/BN531 is available in metric thread sizes and can be used in threaded and unthreaded holes. The adjustable-length feature also makes it ideal for applications where the mounting point may vary.