Round glass beads act as the conductive material for the heat in the Hot Cup. They heat to 100 degrees C or 212 F, which is the temperature of boiling water. Beads may get scratched eventually due to the nicks and abrasion of the instruments being sanitized. We suggest replacing beads every 6 months. To clean beads, rinse off dirt and debris under warm water in a small strainer, dry well before reusing.