Part of the standard issue US Molle II system: the hand grenade pouch.
These are in OCP/Multicam.
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: 8465-01-641-9377
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.