A microwave charcoal filter is located in over-the-range microwaves that are not vented to the outside. The charcoal filter works to absorb unwanted odours in the air while you're cooking. Most top-of-the-line models actually have two filters: a charcoal filter and a grease filter. The LG microwave charcoal filter is genuine and available for use in your microwave, having been obtained directly from the manufacturer. It's much better designed to remove odours from the air that enters your microwave through the vent. It measures about 11 inches in length and a couple of inches in width.