Arduino Pro Mini 328 3.3 V 8 MHz

There are two version of the Pro Mini. One runs at 3.3V and 8 MHz, the other at 5V and 16 MHz.
The ATmega328P has 32 kB of flash memory for storing code (of which 0.5kB is used for the bootloader).
It has 2 kB of SRAM and 1kBs of EEPROM.
The Arduino Pro Mini has a number of facilities for communicating with a computer, another Arduino, or 
other microcontrollers. 
The ATmega328P provides UART TTL serial communication, which is available on digital pins 0 (RX) and 1 (TX). 
The Arduino software includes a serial monitor which allows simple textual data to be sent to and from the Arduino board via a USB connection.
Microcontroller                   ATmega328P *
Board Power Supply           3.35 -12 V (3.3V model) or 5 - 12 V (5V model)
Circuit Operating Voltage   3.3V or 5V (depending on model)
Digital I/O Pins                    14
PWM Pins                            6
UART                                   1
SPI                                       1
I2C                                       1
Analog Input Pins               6
External Interrupts              2
DC Current per I/O Pin      40 mA
Flash Memory                   32KB of which 2 KB used by bootloader *
SRAM                                2 KB *
EEPROM                            1 KB *
Clock Speed                      8 MHz (3.3V versions) or 16 MHz (5V versions)