Just upgraded my system to a Rheem RH1V4821STANJA and I been searching around on which thermostat would be best to upgrade to take advantage of the ODD. I was reading about the air-handler under the section RHIV HIGH EFFICIENCY – ECM MOTOR FEATURES & BENEFITS it says

On-demand dehumidification terminal that adjusts airflow to help control humidity for unsurpassed comfort in cooling mode. External filter required ?

Could someone please explain to me about this terminal and what the required external filter is about and is it something I might want to look into getting ?