The water bubble is for vacation watering, simply fill with water and put in the soil. You have to push the bubble to the lower part of the pot. The soil will remain moist to the level of where the edge begins. It is good if you water the plant before placing a water bubble. Keep in mind that a glass ball can make a focal point for the sun and it can get very hot. Therefore avoid placing your water bubble in direct sunlight.

3.75" diameter x 10" tall $17
2" diameter x 5" tall (mini bubble) $11.95