This Rechargeable Li-ion Battery can be used together with our Power block Cords as an external power source for speedlights. It is an ideal power source for wedding and location photographers. With this power pack, it takes only one second to charge your speedlights at full powers, and provides up to 500 flashes in full brightness. You will find this power pack a big help in many occasions. We provide 4 types of power block cords for different speedlight models: Nikon, Canon, Sony, Metz. You may choose the correct Power block Cord based on your speedlight model to connect with this battery, or you may simply purchase this battery to be used with your current power block cord. With its integrated CPU control circuit and thermo-resistant nylon housing, this Power Block provides both software and hardware protection that combines super performance when it comes to safety and reliability. Delivery includes 1 DC 12V rechargeable Li-ion battery, 1 adapter, and 1 strap. If the built-in battery needs replacement, please contact a professional service outlet to replace it with a new special-purpose battery.