Product DescriptionThe Aero Precision M4E1 Enhanced Upper Receiver is built for AR-15 platform shooters who want a strong, precisely machined foundation for a custom rifle build. This one-piece design integrates the handguard mounting platform with the upper receiver for a clean, rigid setup. Machined from durable 7075-T6 aluminum and finished in black anodizing, it features M4 feedramps, .250 takedown pin holes, and support for barrels up to 1 inch in diameter. Included components consist of the barrel nut and wrench, port door, and forward assist, giving builders a solid starting point for a dependable 5.56x45mm NATO upper assembly.Please note that this upper receiver is not compatible with piston kits. Additional components are required to complete the build, including a charging handle, barrel, handguard, gas block, muzzle device, gas tube, and bolt carrier group.Product Highlights One-piece M4E1 enhanced upper receiver design combines the receiver and handguard mounting platform for added rigidity. Machined from high-strength 7075-T6 aluminum for durability and long-term performance. Includes barrel nut and wrench, port door, and forward assist for a more complete upper receiver setup. Features M4 feedramps and .250 takedown pin holes for AR-15 compatibility and reliable function. Black anodized finish offers corrosion resistance and a clean tactical appearance. Specs Brand: Aero Precision Manufacturer Part Number: APAR600201AC UPC: 815421022339 Product Type: Enhanced upper receiver Platform: AR-15 Caliber: 5.56x45mm NATO Material: 7075-T6 aluminum Finish: Black anodized Feedramps: M4 feedramps Takedown Pin Hole Size: .250 Barrel Support: Accepts barrels up to 1 inch in diameter Included Components: Barrel nut and wrench, port door, forward assist Compatibility Note: Not piston-kit compatible Additional Parts Required: Charging handle, barrel, handguard, gas block, muzzle device, gas tube, and bolt carrier group Disclaimer: We strive to provide accurate and up-to-date product descriptions, specifications, and images; however, errors or omissions may occasionally occur. We are not responsible for any inaccuracies or discrepancies in the content provided. If you notice anything incorrect or unclear, please contact us so we can correct it. When in doubt, we recommend verifying details directly with the product&';s manufacturer.