Pair of Herman Miller Aeron Classic arm springs. Fits all size chairs -A B or C sizes with arms that go left and right . Works for older  classic aerons not meant for newer or  remastered chairs.  I have many Aeron parts so please let me know if you are looking for parts for your chair. I also have B and C size chairs available for sale on ebay. Email me with questions. Shipping is $3.99.