I think I might like the type of humidifier that fills the sound hole a bit better, but these work nicely.

This works well to help keep my guitar humidified.

they are good sponges that work well

These didn't require any extra luggage or shipping since they went right in the case and have worked well in keeping the guitars in good condition.

Inexpensive and works

It has worked great.

A sponge in a zip lock bag with a few holes works well too

So I think the Planet Waves humidifier works well for its intended purpose, but you do have to monitor that you are not over or under utilizing it.

These work well and are a snap to change out

Oasis was a mess and ultimately the crystals quit working or fell out or who knows what.

and I know the importance of humidification to keep your instrument in top shape and these work.