Gikfun Pro Mini Atmega328 3.3V 8Mhz For Arduino (Pack of 3pcs) EK6018x3 Pro Mini Atmega328 3.3V 8Mhz 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) USB connection off board Supports auto-reset