Replacement Seat for Herman Miller Classic Aeron Size B Medium (Black Mesh). 18 x 20.25 x 6 inches. Item Dimensions D x W x H. 18″D x 20.2″W x 5.8H. Recommended Uses For Product. [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. We offer the best prices around on high quality products. Our E-store includes media such as books, movies, music and games while offering electronics, toys, sporting apparel, clothing, tools, general home, garden items and more. We are always working hard to ensure your package arrives as soon as possible. We try our very best to make sure every customer is completely satisfied. If there’s a problem, message us! We’re happy to help.