Vertex MH-360S Compact Speaker Microphone Avoid direct sunlight or air from heaters and the like. Make sure the plug is firmly inserted into the transceiver jack. Although this unit is drip-proof, be sure to wipe drops of water away when the unit is moistened with rain, etc. The microphone should be positioned 2cm to 5cm from the mouth. Compatible with VX-160, VX-180, VX-210A.