The light gray upper roller and clip attach to the upper rack to allow the dishrack to move in and out along the track of the dishwasher. If your dish rack is not moving in and out of the dishwasher properly you may have a broken or missing wheel and it will need to be replaced. The roller and axel is made of plastic and measures 1 1/2” W x 2 1/2” high x 1” deep. This is a genuine OEM part and is sold separately.