Complete your rifle build with this Aero Precision M4E1 Enhanced Assembled Upper Receiver that comes equipped with a Quantum Handguard. These AR15 Upper Receivers by Aero Precision are designed for M4E1 spec receivers and are precision machined. This Aero Precision M4E1 Enhanced Assembled Upper Receiver comes equipped with a Quantum Handguard. The Quantum Handguard is a one-piece, free float design that doesn't limit the mounting capabilities of your accessories. It has a removable 4-slot section for your front sight that you can remove if you wish, and it offers plenty of room for your various KeyMod accessories. Also, this upper receiver is compatible with standard AR15/M4 components and fits most BAR-system handguards. Get all the benefits of a free float design with this complete upper including an M4 feedramp extension, forward assist, and a low profile gas block. Pick up the Aero Precision M4E1 Enhanced Assembled Upper Receiver today to create a powerful weapon platform for all of your keymod accessories.