A micro wireless earpiece together with a wireless microphone helps one to have optimal full comfort hearing with free hand kits over a cell phone.
Most micro wireless earpiece is small enough to fit inside the ear canal thus earning them the dubious name of spy earpiece. They are advertised as if it is meant for covert activities like communicating during a conference or a sales call or worse during exams.
Security guards also use them as it can be used along with any blue-tooth enabled communication device.
Micro wireless earpiece works on the passive vibration principle and hence requires no power. So inevitably, they are light.