CMMG Receiver Extension Nut, Mk4 - 55CA9CB

The CMMG 55CA9CB Receiver Extension Castle Nut is a black matte-finished component designed for securing the receiver extension (buffer tube) on compatible AR-15 and MK4 platforms. It is intended for both repairs and new builds, offering a functional solution for maintaining proper buffer tube attachment. Matte black finish for a durable exterior Compatible with AR-15 and MK4 platforms Used to secure buffer tube assemblies This CMMG receiver extension castle nut is suitable for those assembling or maintaining AR-15 and MK4 rifles, providing a dependable fit for various modern sporting rifle configurations.