Herman Miller Aeron Swing Arm Yoke Adjust up down chair armchair Left Black. This slides onto the internal engine chair, armchair and the color is black. We sell over 100 different used parts. Please let us know if you have any questions. Pre-owned, they show wear, and other discolorations that may need touch up paint, but will still work on your chair. Flip tab works and adjusts up and down. It has some kind of coating on it which you can see in photos five and six. This is for one swing arm yoke for the left side, which are genuine OEM parts for the Aeron furniture line by Herman Miller. 127 W Fairbanks ave, #254 Winter Park, FL 32789.