You can find the Magpul PMAG M3 5.56 40 round Magazine here.

The Magpul M3 PMAG is optimized for the AR15/M4 platforms but has internal and external geometry modifications which permits operation with a range of additional weapons such as the HK 416/MR556A1/M27 IAR, British SA-80, FN SCAR MK16/16S, and others.

New aggressive texture gives the shooter more control of the GEN M3, and a paint pen dot matrix has been added to the bottom panel of the body to allow easy marking by the end user for identification. The M3 has a redesigned flared floorplate to aid extraction and handling of the magazine while providing better drop protection, but is slightly slimmer than the M2 MOE for better compatibility with tight double and triple magazine pouches.

Caliber: 5.56
Capacity: 40 rounds
Color: Black