Used in devices that use lower amounts of energy such as smoke detectors, the Duracell Plus 9V battery is one that requires less frequent replacement. The Duracell Plus 9V battery's reliable performance is typical of the Duracell brand. As well as being typically Duracell in its reliability, it also maintains that reliability for up to ten years in storage. This pack is a single cell pack but is available in bulk quantities at cost effective prices and becoming more cost effective, the more you buy.