Earpiece

https://www.raytalkcomms.com/products/earpiece/

Earpieces for two way radios are suitable professional-grade devices for a wide range of applications that require discrete surveillance and communication. A radio earpiece and mic prevents outsiders from hearing your incoming and outgoing transmissions. Earpieces are the clear choice for government agencies, law enforcement, and security professionals, but they're also ideal in quiet environments such as museums. See our surveillance kits for similar models specific to this purpose.