The build quality of the mousse rings are fine, but they are made of galvanized steel. This is a nickel-based coating that is designed to prevent rust, and is commonly used in construction materials.
The coating process produces an outer layer that can be highly toxic to the human body; special breathing apparatus is required in order to weld it.
After having cleaned the rings very thoroughly before my first use, a grayish-nickel stain was left on the dessert that I had painstakingly prepared...which ended up in the trash, and was replaced by a scoop of ice cream. While embarrassing, it was better than potentially providing a lethal toxin to my guests.
I plan to purchase a length of stainless steel tubing and make my own molds for all future use.