Trion 342479-002 Charcoal Filter Media. Trion charcoal after filter for Trion portable air cleaners. Approximate size 3 1/2 x 10 1/2 x 1/2 inch thick with cardboard edge that sticks out on the 2 short ends. That cardboard edge slides into the slot on the air cleaner to hold it in place. Should be replaced every 90 days.