The Ergo Grips Ergo 4971B Castle Nut, Steel Black for AR-Platform is a robust, precision-crafted component designed to secure your receiver extension with reliable, rugged performance. Constructed in steel and finished in a durable black coating, this castle nut delivers steadfast endurance under the demands of demanding shooting conditions, making it an ideal upgrade for rifle parts and long gun parts inventories. Engineered for seamless compatibility with AR-platform receivers, its clean, compact profile and precision machining support secure torque retention and consistent alignment, contributing to dependable assembly and safe operation. Whether youre upgrading a duty rifle, configuring a precision build, or restoring a trusted platform, the Ergo 4971B provides a trustworthy anchor point for your buffer tube assembly, promoting smooth cycling and reduced wear over time. The design emphasizes compatibility with standard AR hardware while offering a clear, professional aesthetic that blends with other components. Choose this castle nut to enhance your builds structural integrity and performance, backed by Ergo Grips reputation for quality, reliability, and practical, field-ready rifle parts that meet the demands of serious shooters and tactical applications.