Review on HiLetgo Bluetooth Wireless Compatible Arduino by Herthoel Yanda

Fair warning: This adapter is not designed for immediate use with your Arduino. First, the logic circuit runs on 3.3 volts, so you need to use a 3.3 volt logic converter (which is ironic since it draws 5 volts). You'll also need to re-solder pin 34 (which is under protective heat shrink tubing) to regularly get into the setup menu (you don't need to do this if you're using a button, but most of my programs require switching between boards) . If you are not using the original 3.3V voltage, we strongly recommend that you buy another product.