They can be used with any outlet, both vertically and horizontally, by twisting the plug base. Ideal for above counter outlets in small room spaces.  

Plugin Wax Melt Warmer Features includes:

•  Rotatable Base for Horizontal and Vertical Plugs
• Compatible With All Wax Melts
• Perfect for Bathrooms and Kitchens
• 3 Prong Outlet

Directions:

Add scented wax melts to the dish and turn the wax warmer on and enjoy the aroma.