CMMG manufactures high quality parts and accessories for the AR-15 platform. This particular item is a replacement buffer for AR-15's/M4's that are chambered in 9mm luger using a carbine receiver extension.
Features and Specifications:
Manufacturer Number: 90CA9B4
Matte Black Finish
AR-15 rifles chambered in 9mm Luger/CMMG MK9 or similar pattern variant using a carbine receiver extension