The Anti-Fatigue Runner is constructed of EPDM rubber SmartCells feature molded beveled edges that will not curl and a closed cell design that does not absorb liquids or trap odors SmartCells products are designed to provide maximum comfort, safety and fatigue relief for years to come.EPDM rubber creates a durable, functional, and long-lasting product that has excellent resistance to heat, ozone, and weathering as well as a wide range of chemicals including, acids, alkalis, and glycols. EPDM rubber is resistant to compression set as well as autoclavable up to 300F.