W30001 is the only single winder module for hand-wound mechanical watches from Sempre collection, manufactured by Orbita Corporation. It features unique ingenious microprocessor that replicates and controls finger winding action. It senses the increasing resistance as the mainspring is being wound and automatically stops winding when the watch approaches the fully wound state. So this Sempre winder winds, but never overwinds your favorite timepiece. The unit is gorgeously covered with rich black leather. It is powered by a supplied AC adapter or alkaline batteries.