PROTO SHIELD REV3 (ONE SIZE) simplifies the design of custom circuits. You can easily solder TH or SMD ICs in the prototyping area to test them with your Arduino board. The SMD area is designed for up to 24-pin SOIC ICs, and the TH area contains plenty of room for the components you need around your project. You can even attach a mini breadboard (not included) to the proto area for solderless operation. The proto area also includes two power lines (IOREF and GND), two LED pads, and SPI signal breakout pads for boards with SPI only on the ICSP header as Zero.