YZY’s Montgo-9 package is a 3D printable lower receiver designedaround the Montgo-9 upper receiver from MatadorArms. The Montgo-9upper receiver is a monolithic upper receiver for AR-platform firearms,using standard 9MM Glock magazines and does not require the use of abuffer tube.This lower-receiver was heavily remixed from RKSpookware’s UBAR9 lower receiver for AR-9 variant pistol-caliber carbines, which wasremixed from IvanTheTroll’s AR-15 UBAR receiver and uses geometryfrom Not_SpookyGuns’ AR-9 Firebolt platform.While the Montgo-9 can be installed directly onto RKSpookware’sUBAR-9 package without issue, this package removes much of theredundant buffer tower reinforcements that are normally required forfirearms that necessitate the use of a buffer tube. This package has alsobeen overhauled aesthetically and features an extended mag-release foreasier reach. It also removes some extra hardware that is necessary forfront-takedown pin reinforcements found on the UBAR models.