The Luth-AR Modular Buttstock Assembly (MBA) for AR style rifles is designed to replace the standard buttstock on the AR. The MBA-2 Rifle Buttstock is designed to work with a standard A2 rifle style buffer tube in a low-cost, lightweight, strong and high-quality design. Similar to the MBA-1, the MBA-2 is designed for those who do not need the additional adjustability of the MBA-1. The modular design of the MBA Buttstock allows you to configure your buttstock to your specific and personal needs, by adding additional adjustability as needed, or none at all. *NOT interchangeable with carbine/collapsable rifles with telescoping assemblies (6-position tubes). You will need to purchase a MBA-3 or MBA-4 to fit these carbine tubes