Westone"s exclusive in-ear monitor technology combined with Westone"s MICS (Microphone In Control System) deliver an all-in-one entertainment and communication solution for the active user or mobile professional. Get Connected. The IEMs have a sensitivity rating of 114 dB @ 1mW, 20Hz - 16kHz frequency response, and 25 ohms @ 1kHz impedance. They use Westone"s balanced armature, full-range driver design. The microphone is strapped along the main line, and features Westone"s Microphone In Control System (MICS). It also features basic call/end buttons to take or drop calls.