The hexagon collar nut, code EN89DE12, is a specialized fastening component designed for use with studs in the MAN L21/31 engine. Its collar provides a larger bearing surface, improving load distribution and resistance to loosening from vibrations. Engineered for use in high-torque and high-temperature environments, this nut contributes to consistent clamping force, sealing effectiveness, and long-term joint reliability, especially in critical engine assemblies like cylinder and exhaust systems.