Professional Grade AR Upper Receiver Fixture. Robust fixture designed for years of hard use. Quick, intuitive interface that allows rapid building/rebuilding and repair of the entire upper receiver of the AR15/M16/M4 family of rifles/carbines/pistols. Designed to allow all upper receiver parts to be installed or removed without interference. Designed with rail systems in mind, the Device has clearance for most rail systems to allow installation and removal while the upper is securely held. Holds receiver from the inside via the bolt carrier raceway and charging handle raceway by way of a "T" interface. Front and rear lugs are controlled along with the entire bottom receiver flat. Compatible with milspec dimensioned receivers and billet receivers utilizing milspec internal dimensions. The Device does not contact barrel extension and is not caliber sensitive. Accurate Picatinny rail, with enumeration, allows for quick optic set-up or repair. A lanyard is provided to keep parts at-hand and help prevent dropping. An internal spring loaded detent allows for vertical application without loss of control. A2 and M4 rear sight tension spring alignment and removal is built in. Forward Assist removal channel in base. "Bolt carrier" style recesses allows Ejection Port door opening and testing.