SunFounder Ethernet Shield W5100 for Arduino UNO R3 Mega 2560 1280 A057 With this Ethernet Shield, your Arduino board can be used to connect to internet. Can be used as server or client. Directly plug puzzle board, no soldering required. It is directly supported by Arduino official Ethernet Library. It adds a micro-SD card slot, which can be used to store files for serving over the network.