The Aero Precision Ar15 complete lower is the perfect base for your custom AR15 rifle. Works with standard Ar15 components and magazines. FeaturesLower parts kitReceiver extensionAR15 carbine buffer and springMulti-caliber lowerAero Precision Standard Gen 2 Lower Receiver in Anodized BlackThese parts come assembledMOE Version, Includes a Magpul STR Collapsible Stock