The CBP-N2 Compact Battery Pack from Bolt will boost the number of flashes and the recycle time of your compatible SB-900, SB-910, and SB-5000 flash. The CBP-N2 can operate on four or eight AA batteries--alkaline, lithium, or nickel-hydride (NiMH). Lights on the pack indicate Standby, Recycle, or Low Power mode. A thermal protection switch prevents overheating. The CBP-N2 can provide up to 577 flashes per charge, and recycle times as fast as 1.92 seconds. The pack, which weighs just 7 oz without the batteries, can also be attached to the bottom of your camera using the tripod socket.