Miad/moe core storage - Magpul MIAD/MOE Core Storage

Great water resistant stash spot for batteries, ear plugs, etc. fits plenty more than just batteries, store a set or two of ear plugs, a coin battery for the red dot, and a lens cloth. I wouldn't submerge the thing and expect it to keep out water, but it should be fine for a quick dunk or whatever rain can throw at you.