With 16Mhz crystal Power supply jumper to connect external 5V. he USB port is also available in single row pin strip to connect a USB cable (Host) to connect other Devices. Module Size : 3.4cm x 1.8cm/1.33»X0.7» Pin Size : 3cm X 1.2cm / 1.18»X0.47» Supported under Arduino IDE V1.0.5