If you've ever looked closely at the Arduino setup, they love 16MHz. The ATmega328 can actually run up to 20MHz, but back when Arduino got started with the ATmega8, 16MHz was the fastest it could run. So most of the Arduino bootloaders, boards, and IDE only support 16MHz. So here we have a 16MHz resonator
for all your Arudino and ATmega hacking pleasure.