Kettle Composition: Made with high quality tempered borosilicate glass, and food grade 304 stainless steel the epsilon Electic Kettle Collection simply delivers the purest of waters. Boiling Point: The professional temperature controller has a built in automatic shut-off when water reaches boiling point. This precise control allows your epsilon electric kettle to reach the desired boiling point for your water or tea and then safely shut down. The EK also has a keep warm function preserving heat to 85 degrees.