Cartridges fit seamlessly into my homedics ultrasonic humidifier. Have multiple humidifiers in our house and these filters really help in lowering the amount of white dust we have. Much less expensive than the ones sold by humidifier manufacturer.

The inside of my humidifier was covered with a grey slime. There seems to be no way to remove it from the inside of the water canister. They appear to be cheap knockoffs that don't really work.