Product review (4 stars): better yet when installing an over stove microwave vent it ...
I trimmed it to fit . got enough for six filters for a magic chef microwave exhaust fan.  fits behind 7 1/4 x 5 x 1/8 in. metal grease filter. this is a non-vented unit. it helps with smoke.  better yet  when installing an over stove microwave vent it outdoors . next time I will .