ZK MT21 Bluetooth Power Amplifier Board 2.1 Channel DC 12V‑24V Sound Power Amplifier Module for 20‑100W 4‑8Ω Speaker Item Type: Bluetooth Power Amplifier Board Material: PCB Radiator Size: Approx. 36x25x10mm / 1.42x0.98x0.39in Bluetooth Version: 5.0(Unobstructed, 15m/49.2ft) Input Mode: Aux, Bluetooth Number of Channels: 2.1 Channel Input Sensitivity: 500mV Power Amplifier Chip: Domestic Power Amplifier Chip Adaptation Speaker: 20-100W, 4-8Q Protection Mechanism: Anti Reverse Connection, Overheating and Overcurrent, Short Circuit Protection Applicable Power Supply: DC 12~24V 5A or More (Can Not Be Connected to 24V Battery Pack) Output Power: Left and Right Channel <50W, Subwoofer <100W