Common sense dictates that the bigger the fan, the bigger the airflow. But if you run an 80mm fan and a 120mm fan so they produce the same airflow, then the 120mm fan will run quieter than the 80mm fan. This is because the 80mm fan will have to spin much faster than the 120mm fan to be able to maintain the same airflow. This reason alone is why we highly recommend using 120mm fans where possible. This fan adaptor from Nexus allows for a 120mm to be installed in place of an 80 or 92mm fan. This gives you the extra benefit of lower fan speeds and quieter noise levels without any decrease in airflow. A win-win situation!