Herman Miller Aeron Chair Top Activated Gas Cylinder Replacement Part. Replace your worn-out gas cylinder with our high-quality replacement part designed for Herman Miller Classic Aeron Chairs. This top-activated gas cylinder ensures reliable seat height adjustment and smooth travel, providing you with a comfortable sitting experience. Our replacement part meets the high construction industry standard (BIFMA Plus Quality) and exceeds ANSI/BIFMA5.1-2011 standards. Meets the high construction industry standard (BIFMA Plus Quality) for Herman Miller Aeron Chair cylinders. Adjustable height of 6 inches for smooth seat travel from the lowest to highest seating positions. Exceeds ANSI/BIFMA5.1-2011 standards, guaranteeing its load capacity of up to 350 pounds. Heavy-duty piston supporting up to 450 pounds. Why You’ll Love It. This gas cylinder replacement part is specifically designed for Herman Miller Classic Aeron Chairs (Size A, Size B, and Size C models manufactured between 1996 and 2012).