GermGuardian FLT15CB4 Genuine Carbon Filter Replacements for AirSafe Series and AC151 Air Purifier, 4-Pack

I replace this outer filter every three months on a GermGuardian AC3000W. It attaches to a Velcro strip on the inner filter (replaced every 6 months). This outer filter catches a lot of dust and bugs. I live on a farm so we have a lot of both of those.