The Spy Wall Listening Device is the Ultimate when it comes to Partition Spy Monitors. Offering the user the latest technology made from high quality materials. You can use the wall contact Microphone for wall contact situations or you can use the 5inch probe to insert into a drilled hole in a wall. The Spy Wall Listening Device is highly sensitive and is equipped with high quality headphones and an FM receiver for bug transmitter capability. You can even record the sounds and conversations picked up by this Listening Device by using the jack plug output on the face. It has a volume dial and a gear wheel with a 4 stage power incriment.These Spy Devices work on stud walls, steel walls, floors etc but also on Concrete and block walls so these are really advanced.