This is a CMMG Stripped Lower Receiver known as the MK9 chambered in 9MM, model 90CA2F3.
Combine this dedicated 9mm lower with a lower parts kit and buttstock kit to build your favorite lower group. Comes with 9mm bolt catch" feed ramp" and ejector installed.
Features:
Forged 7075 T6 Aluminum
Accepts Standard Colt Pattern 9mm Magazines
Bolt Catch/Feed Ramp/Ejector Installed