The Energy Saver 2 is the size and shape of an AA battery. It substitutes for one of the alkaline batteries in the flash battery comparent. Always start with a fresh set of AA batteries. The result will be much longer lasting AA's.
The Energy Saver is for : Canon 430EZ, 540EZ, 550EX; Nikon SB24, SB25
Reviewed by 2 customers
I use the Quantum ES2 Dummy Battery - Energy Saver for all my celebrity shoots, using the dummy battery with my external flash battery this avoids the main flash from being over loaded and damaged. You will find your battery's in your flash and external battery pack will last longer.
Works anywhere you need a "AA" dummy battery. The price is a little high however it looks like it is made to last. I would like to see some sort of fuse incorporated in the dummy battery for situations where a person might install batteries backwards causing harm to a battery powered device. A fuse might prevent damage to a valuable piece of equipment. I do recommend this product to anyone looking for a quality dummy "AA" battery!