Vibrators very often generate their vibrations using eccentric weights driven by a conventional electric motor, but some use electromagnet coils. Some vibrators are marketed as "body massagers"—although they still may be used, like the ones sold as adult sex toys, for autoeroticism. Some vibrators run on batteries while others have a power cord that plugs into a wall socket. There is also a vibrator that uses the flow of air from a vacuum cleaner to stimulate the clitoris. Modern versions of old musical vibrators synchronize the vibrations to music from a music player or a cell phone. Some luxury brand vibrators are also completely covered in medical grade silicone with no exposed control panels or seams. Although proper cleaning is required for any sex toy, having fewer places for bacteria to grow reduces the chance of infection.