Herman Miller Aeron Adjustable Arm Yoke Support Index chair armchair Black Pair. These attach to the swing arm, go up and down with thumbwheel on their chair armchair. We sell over 100 different used parts. Please let us know if you have any questions. Pre-owned, needs deep cleaning, they show wear, has discolorations that may need touch up paint, but it will still work on your chair. The arm indexes which allow them to pivot in and out do work. Need thumbwheels to adjust. Flip tabs won’t work. This is for one pair of black called graphite adjustable arm yokes with index hardware and new style arm supports that has plastic on the underside and metal above that, and are genuine OEM parts for the Aeron furniture line by Herman Miller. 127 W Fairbanks ave, #254 Winter Park, FL 32789.