Features & Specs: 

WORKS ON CEMENT WALL,LANTER,CONCRETE WALL UPTO 10 INCHES.
Works on wooden walls, doors, windows, steel plates, etc.
Spy Bug with earphones
Volume Dial to amplify sounds
3.5mm Earphone Jack
USB IN
ON/OFF Switch Button with volume Dial
Built In rechargeable battery.

Dimensions: L:43 x Diameter:36 (mm)
Highly Sensitive, carefully adjust audio slowly, as not to cause discomfort to your ear-buds

Technically speaking the device is pretty simple. It works by amplifying the vibration of audio. Whenever you talk, the voices that are generated are wavebands, these wavebands travel through short and long distance. And when the inspector gadget audio device is switched on, it picks up these wave bands and amplifies them, so that you can listen to them. All you have to do is to put the spying device against the wall, connect the earphones with it and listen to things being said on the other side of the wall. It Works on wooden walls, doors, windows, steel plates, etc, works best when used on barriers that are 6 – 10 inches in thickness. The amplification level can be increased by a dial located at the back of the device. You can listen to all those gossips and murmurs by increasing the amplification level. Now your ears can sneak in to the happenings behind the walls!