Quantums Energy Saver improves the efficiency of alkaline AA batteries for some flashes that require AAs when using the Turbo Batteries. The Energy Saver is the size & shape of an AA battery. It substitutes for one of the alkaline batteries in the flash battery compartment: If a flash normally required 4 AAs when used with the Turbo, insert just 3 AAs & the Energy Saver. The result will be much longer lasting batteries. Not all flashes can take advantage of the Energy Saver (due to their internal circuits). Be sure to use the right model energy saver for your flash. For best results always start with a fresh set of AA batteries.