COOMAX Invisible Secret Spy Nano Wireless Earphone Earpiece for Mobile Phone Headset Microphone Detection This extra small wireless earpiece permits you to receive real time information or communications without being noticed. Earpiece Dimensions: 3x2mm Works with any mobile phone with a 3.5mm jack or with the use of an adapter (not included) Invisible wireless earpiece receives signal by an inductive coil across electromagnetic fields (like a radio) Completely hidden and discreet communication