CYMA Airsoft M5 External Battery Box Case w/ Universal Weaver Mount The NEW CYMA MP5 Style External Battery Box makes storing batteries a breeze for AEG rifles that are wired to the front. This battery case, which features a rugged polymer construction, is ideal for placement on railed M5-type rifles but will fit on any AEG that comes equipped with 20 millimeter weaver rails. The battery box easy open, pull-off lid lets you easily store small type NiCd, NiMH and LiPO batteries, while providing you with ease and access to them at all times. This is a perfect PEQ box that allows ample space for storing the batteries you need for your AEG!