Willdo's Environmental Initiatives
Regular folder cups are made from TPE (thermoplastic elastomer) material.
TPE is a sustainable material that is elastic, lightweight, and reshapeable like rubber, and is BPA-free (bisphenol A, a chemical found in some plastics that is of concern due to its adverse effects on the endocrine system).
Even if you pour hot water into it, no harmful ingredients will be released, so it is safe to use, even with children and pets.