SainSmart 1602/2004/12864 LCD(optional) + UNO/UNO R3/Mega2560/Mega2560 R3(optional) Kit for Arduino (Mega2560, LCD2004 White) Uno is based on the ATmega328. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. UNO R3 is improved version. It has perfect quality and much more performance! In addition, the SainSmart Uno R3 now uses an ATMega16U2 which allows for faster transfer rates and the ability to have the UNO show up as a keyboard, mouse, joystick, etc. No drivers needed for Linux or Mac (inf file for Windows is needed). The SainSmart MEGA 2560 Board for Arduino: This is a microcontroller board based on the ATmega2560. It has 54 digital input/output pins (of which 14 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. Specifications : Input voltage - 7-12V. 54 Digital I/O Pins (14 PWM outputs). 16 Analog Inputs. 256k Flash Memory. 16Mhz Clock Speed. MEGA2560 R3 uses an ATMega16U2 which allows for faster transfer rates and more memory. No drivers needed for Linux or Mac, and the ability to have the Uno show up as a keyboard, mouse, joystick, etc. It also adds SDA and SCL pins next to the AREF. In addition, there are two new pins placed near the RESET pin. One is the IOREF that allow the shields to adapt to the voltage provided from the board. The other is a not connected and is reserved for future purposes.