This product is OK, but the following points for me were not clear from the product description and detract in my opinion.
1. It requires filling with distilled water which the instructions state should be changed every 7 days, which could get very expensive and is a bit of a chore.
2. When filled with water it is not sealed, so if knocked over all of the water would pour out the top of the tube. So, an absolute no no if you have small children around.