Internal core unit for the miad as well as the MOE, MOE+, and moe-k2 grips designed to hold two (2) AA type batteries in a self-contained, water-resistant unit. Included internal spacer provides rattle free storage of either (2) AAA or (2) N size batteries (commonly used for EOTech sights). rubber cap has two sides with marking to identify "spent" Batteries and can be opened with a push of the thumb..