The Duracell Ultra size C battery can be left in storage for up to ten years and will maintain its durable, dependable performance, until it is needed. Powering a multitude of high draining devices that are used everyday, the size C battery is a much required purchase,. With the capability of providing 40% more reliable power than that of the Duracell Plus size C battery the Duracell Ultra size C battery is a recommended choice for those devices that require that extra boost of power.