Uno R3 is the clone one of the latest version of Arduino Uno with an on-board CH340 usb - serial converter chip. Even there are some little differences respect to original one, it is almost the same in terms of usage and software. This provides you a cheaper opportunitiy to get started with Arduino boards. The microcontroller model of this board is the same as the original one (Atmega328). The only difference between microcontrollers is ther package. Original one has a DIP package but the clone one has SMD package microcontroller. We offer working warranty for this product as we offer the for the original one. so, you may trust to use this cheaper clone board. Untill now, we have not seen any problem of using this board but, if you see any problems we offer ralunda or exchange too. Despite being a clone one, there are a pin group (4x GND, 2x 5 V, 2x 3.3 V, 1x RX/TX, 1x SCL/SDA) near to the crystal oscillator and there are external pin holes allow you to solder male headers on the board too. This feature provides a better application experiance for you. Extra - added pins are listed below. Additionally, the product comes with 2 x 20 male-male header for these holes.