New Pneumatic Gas Cylinder for Herman Miller Aeron Chair Chair Lifting Accessories, Black. Listing is for a product new never used CLASS 4 WITH 400N, office chair seat height adjustment pneumatic gas lift cylinder. Stroke (seat travel from lowest to highest seatings). Exceeds ANSI/ standards, based on the specs of this cylinder, it’s load capacity is 350 pounds. Cylinder Diameter: 28mm (“) Column Diameter: 50mm (approx 2″). Cylinder for Size A, B and C Aeron Chair. Offer 5 s satisfaction.