1. .2. It enables you to talk and listen without having to move the radio. Just clip the mic where convenient and use it to listen and transmit.3. Works with mobile radios with 8-pin RJ connector.Compatible Models:For TM-231, TM-241, TM-731A, TM-631A, TM-201A, TM-401A, TM-201B,TM-401B, TM-211A, TM-411A, TM-221A, TM-321A, TM-421A, TM-521A, TM-231A,TM-331A, TM-431A, TM-531A, TM-241A, TM-441A, TM-541A, TM-701A, TM-721A, TM-621A,TM-2530A, TM-2550A, TM-2570A, -4100A, -4000A 8pin Material:ABScolour:blackPackage Contents:1 * Speaker Mic for Only the above package content, other are not included.Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.