Herman Miller Aeron Swing Arm Yoke Pair armchair Polished Aluminum thumbwheel. These slide onto the internal engine chair, on office chair armchair and the color is polished aluminum. We sell over 100 different used parts. Please let us know if you have any questions. Pre-owned, the aluminum needs to be polished, they show wear, and other discolorations, the thumbwheels and arm index hardware pivots still work. This is for one pair of swing arm yokes with both the left and right side, one pair of arm supports with working index pivots, and two working thumbwheels, which are genuine OEM parts for the Aeron furniture line by Herman Miller. 127 W Fairbanks ave, #254 Winter Park, FL 32789.