The Motorola PMMN4024 Remote Speaker Microphone(RSM) is designed for MOTOTRBO digital two way radios. This RSM utilizes innovative windporting technology that suppresses background noise. In howling wind, driving rain and severe weather, windporting technology helps you communicate effectively and hear clearly. It also prevents water from clogging the microphone, which results in clearer transmissions and with a 3.5mm audio jack, this RSM offers discreet message delivery and more operational flexibility by having messages delivered right to your ear.