Replacement Seat for Herman Miller Classic Aeron Size B Medium (Black Mesh). Fits Your Herman Miller Chair – Measuring 20.25 inch Width x 18 inch Depth x 6 inch Height, our Herman Miller Aeron replacement parts are designed to fit any Classic Aeron chair size B. Replace your old chair seat with great ease! Tough & Durable – Our Aeron Seat Replacement parts feature a reinforced, heavy-duty frame to ensure that it won’t break, crack, or get damaged easily. Sit on your new cushion without worries! Sit Comfortably – This seat is made of filament which offers fantastic ventilation, so you can stay cool all day. Our seat’s black mesh fabric also matches the mesh of Herman Miller Aeron chairs. Fuss-Free Installation – No need to call a handyman to put these chair seat replacements in place. This new Aeron chair seat comes with a manual that’ll help you remove and replace your old seat. Ready To Use – With this new Replacement Seat, t’s no need to assemble mesh, and foam required. The seat itself comes ready to install so you’ll only need a few minutes to revamp your Herman Miller Classic Aeron desk chair.