Work on wooden walls, doors, windows, steel plates, etc.<br> Highly sensitive, please adjust the audio slowly and carefully to avoid discomfort to your earbuds.<br> The audio gadget works by amplifying the vibration of audio. When people chat in the room, their voice is only a band, and according to the size of the voice they speak, the band will travel through short and long distances and be amplified and amplified by this device.<br> Colour: Black<br> material: metal<br> Package Contents:<br> 1 x Detector<br> 1 x USB Cable<br> 1 x Circular probe<br> 1 x Needle probe<br> 1 x Headphone<br> 1 x Chinese and English manual<br> Only the above package content, other products are not included.<br> Note: Light 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.