Top-cofrLD Bluetooth CSR4.0 crs8635 amp Bluetooth Audio Receiver Amplifier TDA7492P 25W + 25W digital amplifier board if the speaker is 4 ohms should not exceed 16V supply voltage TDA7492P 25W + 25W Diameter power port are: the outer diameter of the inner diameter 2.1MM 5.5x Bluetooth pairing without a password Board size: 68 (W) X 56 (depth) X 20 (H) mm