The Powerex Precharged MHRAAP4 Rechargeable AA NiMH Batteries (1.2V, 2600mAh) - 4-Pack is a package of 4 AA nickel-metal hydride (NiMH) batteries. They have a voltage of 1.2V and a capacity of 2600mAh, with a minimum capacity of 2450mAh. The batteries are capable of being stored for an extended period of time and still retaining a full or nearly full charge. After a year, for instance, they will retain up to 85% of their capacity. The batteries come pre-charged and can be recharged up to hundreds of times. The purchase of NiMH batteries like these saves you money, since you won't need to buy endless supplies of non-rechargeable alkaline batteries.