This 2-part duct for your New Matter MOD-T printer concentrates the airflow from the bottom vent over the nozzle to improve the printing of overhangs - compare the bunny ears with and without the duct.
UPDATE: Initially printed this on another printer, but I re-printed this on my MOD-t and it works fine!
To get the housing in place, you'll need to unplug the hot-end and then slide the housing in from the back. I've simply used a big rubber band to hold the housing in place, or you could tape it in place. (Or glue it if you are really confident!) The small vent then slides into place.
If you decide you don't want so much airflow over the nozzle, just pull out vent part and the air will blow out the front instead.