The glass he uses is a high strength borosilicate commonly referred to as “pyrex”. Borosilicate glasses were initially developed for scientific purposes, but in recent years has been utilized by artistic flameworkers.
This is quite the unique gift – stick the waterer in any flower arrangement or potted plant, fill the vessel with water, and as the plant needs water, the water will be absorbed in the soil. It will not overwater the plant!!! Amazing. Each waterer is different in design and color.