Feature: 1. Double Layer Design: The development board is safe and reliable and can be extended to a variety of applications. 2. Expansion Pin: The module can expand the GPIO pins on a development board to two, greatly facilitating the reuse of pins for large smart projects, excellent alternative. 3. High Reliability: The development board has a double layer design with pins on both sides for excellent stability and high reliability. 4. Highly Integrated Chip: This development board is a highly integrated chip that provides a complete, self contained WiFi networking solution. 5. For NodeMcu Firmware: This development board incorporates the for NodeMcu firmware to power your development in the fastest way possible. Specification: Item Type: Development Board Material: FR 4 Size: Approx. 63 x 69mm / 2.48 x 2.72in Compatible With: For NodeMcu Lua WIFI V3 expansion board. Package List: 1 x Development Board