B00KVOVSXS Nissin PS8 Battery Pack – Ultra Fast 0.5 to 0.7 Recycle Time – Dual Power Socket Supports 2 Flashes – Compatible with/fits Canon Flashes

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ULTRA FAST – 0.5 to 0.7 flash recycle time
CONNECT 2 FLASHES – dual power output sockets to support 1 or 2 flashes
HIGH CAPACITY BATTERY – 3000 mAh rechargeable NiMh battery provides up to 550 full power flashes; also includes USB port for charging smartphones
RAPID BATTERY REPLACEMENT – battery cartridge design enables you to quickly change batteries during photo shoot
POWER CONTROL – features 1/1, 1/2, or 1/4 regulated power for use with 2 flashes, 1 flash, or power save mode