It's blue! It's thin (0.8mm)! It's the Arduino Pro Mini! This is a 3.3V Arduino running the 8MHz bootloader. Arduino Pro Mini does not come with connectors populated so that you can solder in any connector or wire with any orientation you need. We recommend first time Arduino users start with the Uno R3. It's a great board that will get you up and running quickly. The Arduino Pro series is meant for users that understand the limitations of system voltage (3.3V), lack of connectors, and USB off board.
This board connects directly to the FTDI Basic Breakout board and supports auto-reset. The Arduino Pro Mini also works with the FTDI cable but the FTDI cable does not bring out the DTR pin so the auto-reset feature will not work.
Dimensions: 0.7x1.3" (18x33mm)
ATmega328 running at 8MHz with external resonator (0.5% tolerance)
Low-voltage board needs no interfacing circuitry to popular 3.3V devices and modules (GPS, accelerometers, sensors, etc)