Our Industrial Grade Polyurethane chairs are designed and suited for industrial environments, healthcare and laboratory. They meet and exceed the highest U. S. safety standards, CA117, clean-room class 10, 000, and are warranted unconditionally for ten years. Notice: All our 450# capacity seating has been tested to, and exceed the standards of ANSI/BIFMA testing for that weight, however, we do not recommend it for individuals over 350 pounds, as the gas filled lift cylinder will hold the extreme weight well, but this weight compresses the gas inside the cylinder, causing the seat to go down 1? to 2?. Additionally, we recommend the purchase of glides on chairs carrying heavy individuals, as the chairs could otherwise roll away when being boarded, causing the person to fall.