Made to Fit Only Herman Miller Aeron Size B Chair Will NOT Fit Aeron Size C or Size A Chairs NOT Compatible with Aeron Remastered. Mirra 1 or Mirra 2 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, there'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. 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! 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