This complete upper receiver features the same tried-and-true construction and aesthetics as Aero's M4E1 Threaded Upper Receivers, without provisions for a forward assist. The included ATLAS R-ONE Handguard is designed with size and weight in mind, while still providing plenty of real-estate to accommodate any attachment needs the end user may have. 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.