Nordic Components MXT magazine extension tube 12GA +6. - MXT extension tube for changing magazine extension length and capacity - Features relief groove to eliminate barrel clamp travel and ensure repeatable placement after disassembly - Relief groove is not centered and can be relocated by reversing the tube (thread pitch the same on both ends) - Includes ONLY MXT tube - May require purchase of new magazine spring if you are changing the capacity of your existing extension (shell capacity measured with 2 ¾in shells and may vary with shells of differing length) IMAGE MAY NOT REPRESENT PRODUCTS ACTUAL SIZE