When you're looking for Maxim Defense ingenuity in a new standard AR-9 the MD-9 is your answer. The MD-9 was engineered to fit the growing demand for cutting-edge AR9-style rifles for today's Military and commercial market. Every MDX features our free-floating barrel with our custom handguard for increased comfort and versatility. These handguards provide a monolithic-like upper receiver platform and M-Slot compatibility. - Caliber : 9mm - Barrel Length: 5.8 inches - Thread Pitch: 1/2-28 - Weight: 6.1lb - Overall Length: 20 inches - Material Composition: 7075 Aluminum & tool steel - Finish: Nitride / Type III Anodizing - Stock/Brace Options: CQB Brace