The Motorola PMMN4073 IMPRES Remote Speaker Microphone (RSM) is designed for MOTOTRBO digital two-way radios. This RSM uses innovative Windporting technology that suppresses background noise and IMPRES intelligent audio to provide optimal audio performance and improved gain capability. In howling winds, driving rain and severe weather, Windporting technology helps you communicate effectively and hear clearly. It also prevents water from clogging the microphone, resulting in clearer transmissions. The PMMN4071's compact design provides hassle-free use and its 3.5mm audio jack provides discreet message delivery and greater operational flexibility by having messages delivered directly to your ear.