Works on wooden walls, doors, windows, steel plates, etc. 
Highly Sensitive, carefully adjust audio slowly, as not to cause discomfort to your ear-buds 
This product is being sold as an investigative tools for law enforcement or licensed investigators. Anyone else ordering this device should only be ordering it as a simple toy since MANY COUNTRIES STRICTLY PROHIBIT OWNERSHIP OF bug DEVICES

Description:

 As simple and powerful as possible from a handheld listening device, this audio gadget can let you hear conversations through walls and other barriers. 

So how does it work Simple, you switch on the Inspector Gadget Audio Listening Device, insert the earphones, and then place the audio bug on the wall and listen to what's being said. 
This  audio gadget works by amplifying the vibrations of audio. When people are talking in a room their voices are simply a waveband, and depending on how loud they are talking, the waveband travels short and long distances which are picked up and amplified by this device. 
The sensor on this  audio gadget senses the vibrations hitting the walls, ceiling and floor and amplifies them so that you can listen to whats being said. If the waveband is low, meaning people talking in a lower note, then you can use the dial located at the back of this cool audio gadget to adjust the volume and increase the sensors amplification. It really makes "" more fun and productive. 
Lets face it, no one really tells the truth straight to your face. So why not find out the truth, you will be amazed what people might say when your whether you are in a motel room, hotel room, your apartment or just in the next room the device will let know whats being said.