New Seat Replacement For Herman Miller Classic Aeron Size B MEDIUM. Make Sure your chair is Size B. Tools Included for order after March 29 2022. DON’T ASSUME IF THIS CORRECT CHOICE OF YOUR SEAT. If you’re not sure what Seat Size/Color/Pattern. We can help to get your correct seat and your chair back to working condition again correctly for once. Its very hard to install this New Mesh into the frame, 98% average person cannot install this tight mesh into the frame without proper machine or tools. Trust us on this, seems so easy to re-install mesh back into the frame (true) because your old mesh is so sagging, it does not have a pulling elasticity force any longer. (Just like a pair of an old socks ain’t tight no more).