This chip suite, made of SMD package loading base plate of atmega328P, is 100% compatible with UNO R3 board, and has been pre-installed with BOOTLOADER. Standard pin arrangement, can be used directly, especially on the breadboard, and with the shock part of the components. On the downside, row pins are thicker and sturdier than those in DIP28 packages, requiring a bit more effort if you need to mount them into a DIP28 IC socket.