Part of the standard issue US Molle II system: the ubiquitous double M4 pouch.
These are in ACU/UCP (that grey digital camo that blends in with a gravel pit and grandma's couch)
They fit two M4/M16 magazines grenades.
NSN: 8465-01-525-0606
They feature a velcro closure flap with two molle straps on the back. There is an internal elastic loop to help with magazine retention.
These will be from a variety of makers, but all are genuine US Government issue and in excellent shape.