It’s a low profile SMD design much like the Arduino Pro. They’ve taken advantage of the space saved by the SMD ATmega168 by adding more useful headers.

One digital input connected to the data stream on the J1850-bus and another pin with the encoded data delivered as ASCII hex messages at 115200 baud. Board: Arduino Pro Mini 5V 16MHz ATMega168 ...

Arduino hardware package for ATmega8, ATmega48, ATmega88, ATmega168, ATmega328 and ATmega328PB - triqadafi/TQDFCore_AVR_Minicore ...