A basic necessity, this winder is compact and lightweight. Ideal for use without the need for a plug-in adapter. Equipped with Orbita long-life lithium D cell batteries. Operating on the 8-minute winding cycle, the batteries will last for many years without the need for replacement. Even longer life may be accomplished by using the 12-minute or extended-winding cycle, which is easily selected using the toggle switch located behind the mounting cup.  This is a great and portable option for any discerning watch enthusiast.