This complete upper is equipped with our cutting-edge Minimal Optical Deflection (MOD) 4 Handguard, paired with an 18" .223 Wylde PROOF Barrel. Engineered for excellence, this Barrel has undergone rigorous testing to ensure peak performance and unrivaled reliability. Elevate your shooting experience with this precision-crafted complete upper. The MOD 4 Handguard included with this complete upper receiver features a 7 sided M-LOK interface allows the user to customize this upper to their exact specifications and needs. Lastly, each of the 4 QD sockets on the MOD 4 utilize a steel liner to ensure a higher shear load and longer service life with the continued use of QD swivels. Specifications for Aero Precision MOD4 15 18 Inch 223 Wylde PROOF 5.56x45MM M4E1-T Complete Upper Receiver: Manufacturer: Aero Precision Caliber: 5.56x45mm NATO Overall Length: 26 in Barrel Length: 18 in Gas System Length: Rifle Length Barrel Twist Rate: 1-8 Threads per Inch: 5/8x24 Muzzle Device: A2 Flash Hider Finish: Anodized Gas Block Journal Size-Diameter: .750 in Handguard Length: 15 in Barrel Material: Carbon Fiber Weight: 54 oz Features of Aero Precision MOD4 15 18 Inch 223 Wylde PROOF 5.56x45MM M4E1-T Complete Upper Receiver New enhanced forging that gives the upper receiver a "billet look" New picatinny profile that blends seamlessly with our Enhanced Series Handguards M4 Feedramps .250 takedown pin holes Laser engraved T-marks Includes port door and forward assist installed Full top picatinny rail for optional attachments Quick disconnect sling socket at the 3, 6 and 9 o'clock positions Compatible with low profile gas blocks Compatible with mil-spec AR15 upper receivers and barrels Standard A2 Flash Hider Package Contents: Aero Precision MOD4 15 18 Inch 223 Wylde PROOF 5.56x45MM M4E1-T Complete Upper Receiver M4E1 Threaded Assembled Upper Receiver MOD 4 15in Handguard 18in .223 Wylde PROOF Barrel Low Profile Gas Block and Gas Tube Product comes assembled