The Duracell Plus 9V battery does not need replacing very often as it is the battery you would use in low energy consuming devices such a security systems. It holds 30% more power than a standard Duracell 9V battery and can be left in storage for up to ten years without losing its reliable and durable performance. This pack of 2 is available to buy as a single pack or for the most cost effective purchase they can also be purchased in bulk quantities.