Schumann resonance (SR) are a set of spectrum peaks in the extremely low frequency (ELF) part of the earth's electronmagnetic field specturm.This schumann waves generator with high precise and fine stability, give you a better using experience.You need to connect it with the power by type-c cable, no battery included, which is convenient to use.You can use it in your home to reduce your insomnia, also can use it in the office to improve work efficiency. It has a wide ranges of uses.Easy to operate, you can use it directly after plug in the power, whether you are a novice or an amateur, you can use it quickly.Disk diameter: 82mm / 3.2inPower supplys: Type-c portResonant frequency: 7.8Hz (adjustable)Colour: as shownMaterial: composite materialPackage Contents:1 x Schumann Resonance GeneratorOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.