These are the original plated steel pistons made by AP for the AP/Lockheed LD19 (1.625" diameter) and LD20 (1.75" diameter) calipers. Sold individually (two are pictured to show top and bottom views).
Note: The length of these pistons has varied widely since the introduction of these calipers, and continues to vary from batch to batch. We cannot guarantee the availablilty of any particular length.