Aeron Chair Replacement Seat Mesh Size B Herman Miller. [Compatible with Classic Aeron Size B Only] Designed to fit Herman Miller Classic Aeron Chair Size B Medium. Not compatible with Remastered models. [Full Mesh Seat Replacement] Complete seat assembly with tensioned black mesh to replace worn, sagging, or torn seats. [Exact Dimensions for Proper Fit] Measures 20.25 inches wide x 18 inches deep x 5.8 inches high for accurate alignment with the original frame. [Durable Graphite Mesh] Strong suspension mesh provides firm ergonomic support and maintains airflow during long sitting periods. [Easy Installation] Pre assembled seat includes instructions for straightforward replacement. No additional hardware required. 18″D x 20.2″W x 5.8H. 20.2 “h x 18.0 “h x 5.8 h. Weight: 4.6 lb.