1. materials with guaranteed quality 2. Shumanbo itself does not directly act on audio or video products to improve the quality of sound and image, but on the space environment, the human body's perception of sound and image, and the improvement of the feedback to nature and life 3. It is used for audio-visual space, bedroom, office, space, tea ceremony, meditation space, etc 4. With USB cable 5. Built in 1000MHA battery, which can be once for Product name: Schumann wave extremely low frequency generator Frequency: 7.83HZ Power: 0.5W Output waveform: square wave Colour: Material:metal+plastic Package Contents: 1 x Schumann wave generator 1 x cable Only the above package content, other products are not included. Note: Light reflection 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.