Thank you for viewing. This is a Schumann resonance generator. The Schumann resonance frequency is said to easily resonate with human brainwaves (especially alpha and theta waves), and is said to be effective for relaxation and improved concentration. Color: White LED indicator: Green Design: Compact rectangular design Function: Schumann resonance generation Power: 3 AA batteries Comes with a cover (photos 9 and 10) so you can carry the generator around or hang it somewhere. To operate, simply press the button (photo 3, right side). The green LED light will blink when it's working. Effective within 2 meters of the generator. *Batteries not included I am selling this because I have another similar device. Please understand that this is a used item before purchasing.