Check the listing for details. For Herman Miller Classic Aeron Chair Lumbar Pad Support Size B Medium Black New. Color: Black, Condition: New. Listed at 12.70 USD. For Herman Miller Classic Aeron Chair Lumbar Pad Support Size B Medium Black New Fitment:Helps prevent back pain by supporting your lumbar regionFor Classic Aeron Chairs (Sizes B), Classic Aeron Stools, and Classic Aeron Side ChairsLumbar Pad Size B has 17 ridges - 20.25 inches wide. 2 bumps. Packing list 1 x Lumbar Back Support ShippingAll items will be shipped out in 1 business day, no expedited service available.We ship our items to USA only(Does NOT include Hawaii, Alaska or Puerto Rico, PO Boxes/APO's). Shipping Notes:We use multiple warehouses and will select the nearest warehouse for delivery according to your order address and our inventory, Thank you for your cooperation. Contact usAny Questions, Just feel free to contact us on eBay. We will reply you in 1 business day. How Can I Tell Which Size Aeron Chair I Have?1. Place your fingertips under the frame edge near the top center of the back frame near the Herman Miller stamp.2. Press under the edge until you one or more bumps.3. Count the number of bumps vith your fingertips to determine the chair size - one bump is an "A" size chair, two bumps a "B" size chair and three bumps organized in a triangle is a "C" size chair.