RECHARGEABLE 4 CHANNEL WIRELESS MICROPHONE SYSTEM PRO: ZERFUN MU-898 UHF Rechargeable Wireless Microphone System that comes with four rechargeable handheld metal cardioid microphones and metal receiver box with with Independent Volume Control & ECHO & Bluetooth. Perfect for home karaoke, meeting, party, church, DJ, wedding, and much more. Featured with automatic frequency scanning and automatic transmitter setup for easy synchronization between transmitter and receiver. METAL RECEIVER BOX WITH INDEPENDENT VOLUME CONTROL & ECHO & BLUETOOTH: The devices and the chassis for the receiver are made from metal. Receiver Box has one Mic Input and Mic Vol Control for Wired Microphone; Wireless Mic-A & Mic-B & Mic-C & Mic-D Independent Volume Control; Microphone Adjustable ECHO Function; Bluetooth Function to use Receiver Box as a Bluetooth Receiver to play background music(Turn on your device's Bluetooth, search "X168" and connect; BT Range about 32 Feet). BATTERY INFO & TRANSM