Machined from 6061-T6 Aluminum, the R-ONE line of handguards are designed with size and weight in mind, providing the perfect handguard for your lightweight build. Aero's proprietary ATLAS attachment system is a durable and dependable mounting platform, maintaining a slim profile while still providing the strength and stability customers have grown to love from Aero Precision handguards. The Aero Taper Lock Attachment System (ATLAS) is both functional and aesthetically pleasing. It features 2 mirrored tapered locking nuts that provide evenly distributed clamping pressure across a custom engineered barrel nut with use of a turnbuckle screw. A ratcheting detent further secures the design while providing positive registration during installation. By design, the even pressure of the ATLAS system avoids distortion of the handguard often seen with current applications during installation. All hardware mounting parts are included with the purchase of an ATLAS Handguard. ATLAS Handguards are designed to match seamlessly with Aero's M4E1 Threaded Upper Receivers. Additionally, they are compatible with any Mil-Spec AR-15 upper receivers as well. However, they may not be compatible with billet upper receivers due to indexing tabs. ATLAS Handguards are designed to match seamlessly with Aero's M4E1 Threaded Upper Receivers. Additionally, they are compatible with any Mil-Spec AR-15 upper receivers as well. However, they may not be compatible with billet upper receivers due to indexing tabs. Compatible with AR308 upper receivers and barrels. NOT Compatible with M5E1 Enhanced Upper Receivers. ATLAS Handguards are designed to match seamlessly with Aero's M5 (.308) Threaded Upper Receivers. However, they may not be compatible with billet upper receivers due to indexing tabs.