Aero Precision M4E1 AR15 .223 Wylde 18 inch Fluted ATLAS R-ONE M-LOK Upper Receiver Rifle Length 1-8 Twist 1/2x28 A2 Flash Hider Anodized Black. The R-ONE handguards are designed with size and weight in mind while still providing plenty of real-estate to accommodate any attachment needs the end user may have. Our 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. Specifications for Aero Precision M4E1 AR15 .223 Wylde 18 inch SS QPQ ATLAS R-ONE M-LOK Upper Receiver: Manufacturer: Aero Precision Caliber: .223 Wylde Barrel Length: 18 in Barrel Profile: SPR Gas System Length: Rifle Length Barrel Twist Rate: 1-8 Firearms Threads Per Inch: 1/2x28 Handguard Type: Free-Float Muzzle Device: A2 Flash Hider Gun Model: AR-15 Fabric/Material: 7075-T6 Aluminum Gas Block Journal Size-Diameter: .750 in Handguard Length: 15 in Handguard Style: M-LOK ATLAS R-ONE Gun Rail: M-LOK Gun Type: Rifle Gun Make: AR Platform Weight: 68.5 oz Magazine Included: No Condition: New Country of Origin: USA Threads per Inch: 1/2x28 Features of Aero Precision M4E1 AR15 .223 Wylde 18 inch SS QPQ ATLAS R-ONE M-LOK Upper Receiver: M4E1 Threaded Upper Receiver Features: 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 ATLAS R-ONE Handguard Features: 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 1.3" Inside diameter 1.5" Outside diameter Compatible with mil-spec AR15 upper receivers and barrels Learn More about our NEW ATLAS Handguards 18" .223 Stainless Steel Rifle Length Barrel Features: .223 Wylde 18" Rifle Length Barrel 1/8 Twist 416R Stainless Steel Bead Blasted Finish .750 gas block journal Rifle length gas system M4 Feed Ramp Extension HP and MPI tested Standard A2 flash hider Package Contents: Aero Precision M4E1 AR15 .223 Wylde 18 inch SS QPQ ATLAS R-ONE M-LOK Upper Receiver M4E1 Threaded Assembled Upper Receiver ATLAS R-ONE Handguard of choice 18" .223 Wylde Rifle Length Stainless Steel Barrel Low Profile Gas Block and Rifle Length Gas Tube Product comes assembled What firearm models does the manufacturer say Aero Precision M4E1 AR15 .223 Wylde 18 inch SS QPQ ATLAS R-ONE M-LOK Upper Receiver is compatible with? The manufacturer says that Aero Precision M4E1 AR15 .223 Wylde 18 inch SS QPQ ATLAS R-ONE M-LOK Upper Receiver is compatible with AR-15Aero Precision APAR700705M51: M4E1 Threaded .223 Wylde Complete Upper Receiver 18in Fluted Barrel 1-8 Twist A2 Flash Hider ATLAS R-ONE Handguard Black Anodized