The Aero Precision M4E1 Complete Upper Receiver has an MLOK handguard.
That is correct, this complete upper features the M4E1 Enhanced upper receiver.
• VG6 Precision GAMMA 9mm Muzzle Brake/Compensator Hybrid
The Aero Precision M4E1 Complete Upper Receiver 5.56 Mid Barrel uses a 1/7 twist with a drilled gas port and .750 gas block journal.
The handguard is removable but the upper receiver is the Aero Precision Enhanced upper and will only fit their enhanced handguards.
It is 14.5”. It is clearly stated in the title.
The barrel length for this upper is 14.5".
Per Aero's website for this one: "The muzzle brake that comes with this complete upper receiver is NOT pinned nor welded to this barrel. Per the National Firearms Act, the muzzle brake MUST be pinned and welded to achieve the necessary 16" as defined by the ATF for a rifle build."