Feature: 1. BLUETOOTH 5.0: Digital power amplifier module features Bluetooth 5.0 with a transmission range of up to 49 feet (unobstructed). Features a 3.5mm/0.1in AUX sound input jack. 2. MORE LAYERED SOUND: Bluetooth power amplifier board by adjusting the high and low frequency knobs of for ZK MT21, you can make the sound more layered and the bass more shocking. 3. CONVENIENT TO USE: Sound power amplifier board is easy to use, the DC adapter (plug size 5.5x2.1mm / 0.2x0.1in) on the market can basically meet the needs of for ZK MT21 Bluetooth power amplifier board. 4. MULTIPLE PROTECTION MECHANISMS: Amplifier board has various protection mechanisms to ensure its safe operation. It has short circuit protection, over current, overheat and anti reverse protection. 5. THOUGHTFUL DESIGN: When overload occurs, Bluetooth digital power amplifier module will report the fault condition to the processor to preserve itself from damage. Specification: Item Type: Bluetooth Digital Power Amplifier Module Material: PCB Sound Input: AUX And BT Voltage: DC12-24V Channel: 2.1 (50W, 50W, 100W) Bluetooth: 5.0 Current>9A. Package List: 1 x Bluetooth Digital Power Amplifier Module2 x Housing1 x DC Conversion Plug1 x Screwdriver4 x Studs13 x Screw Note: If your existing DC power plug is not 5.5x2.1mm / 0.2x0.1in, there is no problem because we include the DC conversion plug in the product.