The dishes fold from flat pieces of precut polypropylene (food grade). The coloring as well is food-grade.
They hold cold or hot food or liquid. They are easy to clean, and come in four colors.
The company's environmental policy is on their website here.
And if I've convinced you that you need to have some of these neat conversation starters for your next party or picnic, this link tells you where to buy them, for a few dollars apiece.