A double watch winder is a device designed to hold and wind two automatic watches simultaneously. It mimics the natural motion of the wrist by rotating the watches in various directions and at customizable speeds, keeping the watches powered and running accurately when not being worn.

Key features of a double watch winder include:

1. Capacity to wind two watches at once, which is convenient for collectors or owners of multiple automatic watches.
2. Multi-directional winding options (clockwise, counterclockwise, or bi-directional) to suit different watch models' requirements.
3. Adjustable settings for Turns Per Day (TPD), allowing customization based on the specific winding needs of each watch.
4. Cushions or cuffs that fit various watch sizes, securing them during rotation.
5. Power options including batteries or AC power adapters for flexible placement.
6. Often features a protective cover to shield watches from dust and damage, and may include additional storage compartments.

Double watch winders are especially useful for those who frequently switch between multiple automatic watches and want to avoid manually resetting time, date, or other complications. They also serve as elegant display cases, combining functionality with style.