It's hurt in the butt to find battery for those MOD stock. The only brand that I'm sure can hold the battery is the king arm version which come with Intellect 9.6 V 1400 mah with the stock, you can get from airsoftparts.ca and don't forget to get extra battery.
I suggest you go to crane stock since crane stock can be store up to 9.6 V 4200 mah which I'm using on mine right now.
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