An anvil cap for providing secure anastomosis in a circular staplers in which the anvil cap has a movable inner shaft, a command wire connected to the movable inner shaft so as to cause a pulling movement to be applied to the movable inner shaft, a plurality of upper wings pivotally mounted to joint points on the movable inner shaft so as to be openable in relation to the movable inner shaft, and a plurality of lower wings cooperative with the plurality of upper wings such that the plurality of lower wings open when the plurality of upper wings apply pressure to the plurality of lower wings.
