This air filter replacement cartridge fits the following aeration pumps. Kasco 1/4 HP, 1/2 HP, and 3/4 HP compressors. Airmax 1/4 HP, and 1/2 HP. Easy Pro ERC 1/4 HP, 1/2 HP, 3/4 HP compressors. Note: Easy Pro SRC compressors use a different filter (model GAFE) It's important to replace this filter regularly to insure that your aeration pump is performing at it's best.