Basic all purpose utility pouch. I use it to store my kill rag, gloves, water bottle, as well as overflow magazines (ie: more than my typical load), and empty mags if I don't have a dump pouch. When its empty its great because its flat and doesn't block you from going prone. I have mine set up on my rig so that its slightly off center to my right so that it doesn't get in the way of my climbing harness as well as so when it is full and I go prone it doesn't prop me up too much or crush anything. Velcro is nice and if you REALLY need to stuff allot in the straps are very adjustable and hold whatever you might need. Overall excellent. My pro's and con's summarize my thoughts on it and add a few other points.
-Very flat profile when not filled up or empty
-Velcro + Straps to snap shut are very useful
-Velcro on the front for patches (although depending on where you put it sort of a strange spot for a patch!)
-Great alternative for a dump pouch attached to your rig
-Holds pretty much anything, I can fit 6 M4 mags in it
-The clips to the straps dangle when not in use and if you go prone they tend to stab into you, just a reminder. Also they sometimes get caught on things.
-For smaller rigs its harder to find the right spot to allow you to go prone.
-While it fits M4 mags, generally its easier to use dedicated M4 mag pouches as youll likely end up fumbling for mags!