Unidirectional microphone with a VHF receiver. Offers a wide frequency response and high sensitivity. Battery operated - DC 9V battery (NOT included). Compatible with Singing Machine karaoke machines. Only use one SMM107 per machine or receivers will cause interference. Mic dimensions: 2"W x 2"L x 9.4"H. Receiver dimensions: 3.9"W x 1"L x 2.8"H. Includes the wireless microphone and a 6.3mm plug with a extra 3.5mm adapter.