Some surfaces work better than others and density / thickness can also restrict its performance. We have received varied results as it depends entirely on the surface you use and many other factors such as distance and volume. Place the Sonde contact microphone to the surface of interest and listen it has variable gain and volume settings. You may need to experiment further with the position for better results and we can not guarantee results first time every time. We guarantee it will hear audible sound through any door or single brick / cavity walls.Unless it is faulty not hearing through doors, windows, internal walls etc. HIGHEST SENSITIVE LISTEN THROUGH WALL / CEILING CONTACT & PROBE MICROPHONE SET. THIS IS A PRIVATE LISTING DUE TO THE NATURE OF THIS PRODUCT.
F-999B professional listen through wall spy ear is a highly sensitive contact and probe microphone amplifier system. Both microphone and amplifier are built into a strong metal housings for durability. Enhanced quality sound and performance capable of listening to conversations in adjoining rooms and houses. High quality earbuds a built in lithium battery and all accessories needed to achieve the job. The highest sensitive contact microphone available with superior detection ability using best quartz crystal piezo.Penetrable surfaces: Cement, Metal, Wood, Iron, Glass, Plastic, Brick. Working time: Continuos monitoring up to 24 hours. Four audio channel: 1200Hz, 800Hz, 200Hz. Maximum gain amplification: 20000 times. Battery type: 3.7v lithium battery. Record line output: 2.5mm stereo Jack socket. 2.5mm-3.5mm stereo record lead. The item "SPY LISTENING DEVICE F999B EAR BUG WALL DETECTION SUPER SENSITIVE EAVESDROPPING" is in sale since Friday, August 24, 2018. This item is in the category "Home, Furniture & DIY\Smart Home & Surveillance\Home Surveillance\Home Surveillance Parts & Accessories\Other Surveillance Parts & Accessories". The seller is "micronic007" and is located in Winchester. This item can be shipped worldwide.