Part of the standard issue US Molle II system: the ubiquitous hand grenade pouch.
These are in ACU/UCP (that grey digital camo that blends in with a gravel pit and grandma's couch)
They fit standard M67 grenades, but will also work with MkII and M26 grenades as well. And plenty of other items too, be it skittles or a bunch of ball bearings.
NSN: 8465-01-525-0589
They feature a metal snap closure flap with two molle straps on the back. There is an internal loop to place a grenade spoon through for better retention.
These will be from a variety of makers, but all are genuine US Government issue and in excellent shape.