CHAIR MASTER ESD line of Industrial Grade Polyurethane chairs and stools were designed for industrial, healthcare and laboratory environments using proper grounding, conductive, and dissipative static control materials. Ergonomic design for comfort during extended use. Extremely Durable and Easy to Clean. All Polyurethane chairs meet and exceed ANSI/BIFMA standards. Clean-room class 10,000. ANSI/ESD-STM-12.1-2006, Fed Std.209E and ISO 14644-1 requirements (Class 10/ISO Class 4). Rated up to 450 pound seating capacity. Please Note: Caution for use by individuals over 350 pounds should note that the seat may compress an additional 1"-2". Warning if casters are used, the chairs can roll away when being boarded, causing harm to the individual.